﻿Abudari, K. and K. N. Raymond (1992). "Coordination Chemistry of Microbial Iron Transport .45. Synthesis and Characterization of Chiral Isomers of Tris(1-Oxo-22(1h)-Pyridinethionate)Iron(Iii), Chromium(Iii), and Cobalt(Iii) Complexes." Journal of Coordination Chemistry 26(1): 1-14.
	Among the chelating functional groups found in the microbial iron-transport agents called siderophores are hydroxamate, catecholate, and thiohydroxamate. The synthesis and properties of several chiral ligands containing 1-hydroxy-22(1H)-pyridinethione are reported. The synthesis and properties of ferric, chromic and cobaltic complexes of these ligands are reported as well. The Cr(III) and Co(III) complexes give electronic absorption spectra which show the two expected d-d transition for d3 and low-spin d6 octahedral complexes superimposed on very broad ligand transitions. Two absorption maxima are also seen in the electronic spectra of the ferric complexes, and which appear to be charge transfer transitions. These spectra resemble those of corresponding thiobenzohydroxamate complexes. Since the ligands are chiral, four diastereomers are possible, but only one isomer has been observed for each complex. All complexes seem to have the cis (or facial) geometry, with C3 point symmetry, and both configurations. LAMBDA and DELTA, have been observed. The chirality of the complexes is assigned based on the signs of the CD bands of the low-energy transition in CR(III) and CO(III) d3 low-spin d6 systems, respectively, and by comparing the shape and signs of CD bands of these complexes with those of the resolved optical isomers of tris(thiobenzohydroxamato)iron(III), chromium(III) and cobalt(III).

Anzai, N., et al. (2006). "Light‐induced formation of curved needle texture by circularly polarized light irradiation on a discotic liquid crystal containing a racemic chromium complex." Liquid Crystals 33(6): 671-679.
	
Anzai, N., et al. (2001). "Chirooptical Control of Liquid Crystalline Textures Containing Chromium Complex by Irradiation of Circular Polarized Light." Chemistry Letters 30(9): 888-889.
	A cholesteric texture was induced in the liquid crystal (a mixture of N-(4-ethoxybenzylidene)-4-n-alkylanilines doped with (R)-(+)-1,1′-bi-2-naphthol and racemic chromium tris(3-butyl-2,4-pentanedionate) (Cr(3-Buacac)3) by the irradiation of right circular polarized light (r-CPL) and resulting chiroselective photoinversion of Cr(3-Buacac)3. After irradiation of left circular polarized light (l-CPL), the cholesteric fingerprint texture was erased.

Anzai, N., et al. (2003). "Light-induced control of textures and cholesteric pitch in liquid crystals containing chromium complexes, by means of circular and linear polarized light." Liquid Crystals 30(3): 359-366.
	
Benedetti, M., et al. (1999). "The effect of pressure on circular dichroism spectra of a chiral helicoidal chromium complex." Physica B 265(1-4): 203-207.
	The effect of pressure on circular dichroism (CD) spectra of the octahedral chiral Lambda- and Delta-tris-[cyclic O,O',1(R),2(R)dimethylethylene dithiophosphato]chromium(III) complexes, Lambda- and Delta-CrC(R,R)bdtp](3), in the solid state has been studied. The pressure range investigated was 0-4 GPa. A method for measuring CD spectra under pressure is described. Results on polycrystalline samples in nujol indicate that the configuration at the metal centre of the chiral chromium complex inverts from the Delta- to the Lambda-form, which eventually is the most stable at high pressure. (C) 1999 Elsevier Science B.V. All rights reserved.

Benedetti, M., et al. (1999). "Configurational equilibrium and CD spectra under pressure of chiral octahedral complexes: Lambda- and Delta-Cr (-)(R,R)bdtp (3)." Enantiomer 4(1): 63-66.
	We have studied the effect of pressure on the configurational inversion reaction at the metal centre of the chiral tris-{cyclic O,O'1(R),2(R)-dimethylethylene dithiophosphato} chromium(III) complexes, A(-)(589)Cr[(R,R)bdtp](3) and Delta(+)(589)Cr[(R,R)bdtp](3), in solutions of different solvents. We have observed positive or negative Cotton effects, assigned to the (4)A(2) --> T-4(2) transition of the metal ion in the visible region, and their evolution on increasing pressure. At equilibrium and at room conditions one observes a prevalence of the Delta-(R,R)(R,R)(R,R) diastereoisomer in CHCl3 or CH2Cl2 and of the Lambda- one in THF. On increasing the pressure a change in the inversion equilibrium occurs, producing an increase in the concentration of the Lambda-(R,R)(R,R)(R,R) form in all solvents.

Biscarini, P., et al. (2006). "Transfer of chirality in complexes with D-3 symmetry: Kinetics of the formation reaction of chiral tris[O,O '-bis(2-methylbutyl)-dithiophosphato]chromium(III) complexes (Lambda,Delta)-[Cr{(+/-)-Mebdtp}(3)], Delta-(+)(589)- and Lambda-(-)(589)-[Cr{(+)-(S)(S)-Mebdtp}(3)]." European Journal of Inorganic Chemistry(16): 3167-3176.
	The formation reaction of chiral racemic and diastereoisomeric title complexes, (Lambda,Delta)-[Cr{(+/-)-Mebdtp}(3)] and Lambda-(-)(589)-[Cr{(+)-(S)(S)-Mebdtp}(3)], was monitored by absorption, UV/ Vis, and circular dichroism, CD, spectroscopy, in the presence of either an excess of the racemic, (+/-)-Mebdtp(-), or the enantiopure ligand, (+)-(S)(S)-Mebdtp- = O,O'-bis[(+)-(S)-2methylbutyl] dithiophosphate ion, at 25 degrees C in various solvents (ethanol, tetrahydrofuran, chloroform/ethanol, 9:1) and at various pH values and reactant concentrations. The kinetics of the formation reaction of the racemic complex, (Lambda,Delta)[Cr{(+/-)-Mebdtpl(3)], shows three consecutive reaction steps. The relative pseudo first-order rate constants depend in different ways on the ligand and H+ concentrations. Circular dichroism measurements during the formation reaction using the enantiopure ligand, as well as in the final equilibrium state, show a prevalence of the Lambda-(-)(589)-[Cr{(+)-(S)(S)-Mebdtp}3] over the Lambda-(+)(589)-[Cr{(+)-(S)(S)-Mebdtp}(3)] diastereoisomer in all solvents used. A mechanism is proposed which involves two parallel pathways each consisting of three consecutive reactions of solvent substitution by a chiral chelated ligand, interconnected by some reversible inversion reactions to obtain in solution the thermodynamic and kinetic Lambda-(-)(589)-[Cr{(+)-(S)(S)-Mebdtp}(3)] as the major diastereoisomeric compound. From the equilibrated solution the more stable solid (Lambda,Delta)-[Cr{(+)-(S)(S)-Mebdtp}3] crystallizes as a ca. 1:1 compound of a pair of the two diastereoisomers, undergoing a crystallization-induced second-order asymmetric transformation. Lambda-[Cr{(+)-(S)(S)-Mebdtp}3] is the thermodynamically stable diastereoisomer in the solid state, though in solution this inverts to the more stable Lambda-(-)(589)-[Cr{(+)-(S)(S)Mebdtp}3].

Biscarini, P., et al. (1995). "Chiral Discrimination of Complexes with D-3 Symmetry - Synthesis and Characterization of Tris(O,O'-Bis[(+)(S)-2-Methylbutyl] Dithiophosphato)Chromium(Iii) Complexes (Lambda-Delta)(Cr[(+)(S)(S)Mebdtp](3)) and Lambda-(-)(589)- and Delta-(+)(589)(Cr[(+)(S)(S)Mebdtp](3)) and Crystal Packing of Racemic Tris(O,O'-Diethyl Dithiophosphato)Chromium(Iii), Cr[Ddtp](3)." Inorganic Chemistry 34(18): 4618-4626.
	Synthesis of the title chiral complex (Lambda Delta){Cr[(+)(S)(S)Mebdtp](3)}, with (+)(S)(S)Mebdtp(-) = (+)[(S)-(CH3CH2-CHCH3CH2O)(2)PS2](-), O,O'-bis[(+)(S)-2-methylbutyl] dithiophosphate ion, as the ligand, was accomplished in solution with various solvents giving rise in all cases to a higher production of Lambda-(-)589 {Cr[(+)(S)(S)Mebdtp](3)} diastereoisomer than Delta-(+)(589){Cr[(+)(S)(S)Mebdtp](3)}. The formation reaction was followed by absorption and CD spectroscopy. The Lambda-(S,S)(S,S)(S,S) diastereoisomer proved to have higher stability in all the solvents employed (ethanol, acetone, acetonitrile, benzene, dichloromethane, chloroform, and water). Crystal packing forces seem to favor an equal mixture assembly of Lambda- and Delta-{Cr[(+)(S)(S)Mebdtp](3)}, as is evident from CD characterization of the solid precipitated from solutions with a slight excess of the Lambda(-)-isomer. Configurational inversion was observed in solution and even in the solid state after a long time if the solid was kept at higher temperature and under vacuum, although the chirality favored was different in the two phases. The molecular structure and crystal-packing mode of the related title complex {Cr[ddtp](3)}, ddtp(-) = (C2H5O)(2)PS2-, (C12H30CrO6P3S6, formula weight 607.64) were determined from single-crystal X-ray diffraction data and refined by full-matrix least squares methods to R = 0.065. Crystals are monoclinic, with a = 14.512(8) Angstrom, b = 13.657(3) Angstrom, c = 14.350(2) Angstrom, beta = 90.42(3)degrees, V = 2844(2) Angstrom(3), Z = 4, and space group C2/c (No. 15). The crystals contained a racemic mixture of Lambda- and Delta-Cr[ddtp](3) enantiomers. The discussion based on the structural information of this compound extends to chiral discrimination in the formation reaction, configurational inversion reaction, molecular structure, and crystal packing of (Lambda Delta){Cr[(+)-(S)(S)Mebdtp](3)}.

Bosnich, B. (1969). "Application of exciton theory to the determination of the absolute configurations of inorganic complexes." Accounts of Chemical Research 2(9): 266-273.
	
Brandl, T., et al. (2018). "Chiral macrocyclic terpyridine complexes." Chemical Science 9(15): 3837-3843.
	The syntheses of novel chiral M(ii) bis(terpyridine) cage complexes Fe(L1)2-c and Ru(L1)2-c are described. The extraordinary design of the precursors Fe(L1)2 and Ru(L1)2 allows perfect preorganization for the final closing step. Due to the rigidity of the spacers between the two terpyridine moieties, the two isolated enantiomers barely racemize at room temperature in solution. The stable and axially chiral bis(terpyridine) Fe(ii) and Ru(ii) complexes were fully characterized by NMR-spectroscopy, UV-Vis spectroscopy, electrochemical measurements, high resolution mass spectrometry, circular dichroism measurements, and X-ray structural analysis.

Cortijo, M., et al. (2017). "Synthesis, Spectroelectrochemical Behavior, and Chiroptical Switching of Tris(β-diketonato) Complexes of Ruthenium(III), Chromium(III), and Cobalt(III)." Inorganic Chemistry 56(8): 4555-4567.
	
Dee, C., et al. (2019). "Strong Circularly Polarized Luminescence of an Ocrahedral Chromium(III) Complex." Chem. Commun.: 13078-13081.
	
Dotz, K. H., et al. (1997). "Axial-chiral metal carbenes: Synthesis and structure of 1,1-binaphthyl-derived carbonyl-carbene complexes of chromium." Chemische Berichte-Recueil 130(11): 1605-1609.
	Axial-chiral mono-and biscarbene complexes of chromium containing the 1,1-binaphthyl skeleton have been obtained in both racemic and enantiopure forms in a one-pot reaction starting from lithiated 2,2-dimethoxy-1,1-binaphthyl (1) and hexacarbonyl chromium via the Fischer route. An X-ray structure analysis of the biscarbene complex 2 reveals that the biscarbene functionalization significantly increases the dihedral angle defined by the biaryl planes. The enantiopure complexes have been characterized by CD spectroscopy.

Emeis, C. A. and L. J. Oosterhoff (1967). "Emission of circularly-polarised radiation by optically-active compounds." Chemical Physics Letters 1(4): 129-132.
	Circular polarisation is shown to occur in fluorescence (trans-β-hydrindanone) and in phosphorescence (Cr(en)3(ClO4)3). Dissymmetry factors may differ considerably from those measured in adsorption. The theoretical basis of the effect and its possibilities for studying excited states are discussed.

Fan, J. and T. Ziegler (2008). "On the Origin of Circular Dichroism in Trigonal Dihedral Cobalt (III) Complexes of Unsaturated Bidentate Ligands." Inorganic Chemistry 47(11): 4762-4773.
	
Furuno, Y., et al. (2007). "Linkage effects of chromium(III) acetylacetonato units on chiral induction of liquid crystal phases." Journal of Physical Chemistry B 111(3): 521-526.
	The linkage effects of polynuclear metal complexes on chiral induction have been studied by application of the chiral oligomers of acetylacetonato chromium(III) units as a dopant, inducing chiral nematic phases. The compounds were prepared by reacting [Cr(acac)(3)] (acac = acetylacetonato) and 1,1,2,2-tetraacetylethane (taetH(2)) in solid phase at 160 degrees C. Binuclear diastereomers were separated on a silica gel column, followed by chromatographic resolution on a chiral column packed with an ion-exchange adduct of Delta-[Ru(phen)(3)](2+) (phen = 1,10-phenanthroline) and synthetic hectorite. An enantiomeric pair (Delta Delta- and Lambda Lambda-[Cr(acac)(2)(taet)Cr-(acac)(2)]) and a meso species (Delta Lambda-[Cr(acac)(2)(taet)Cr(acac)(2)]) were identified. The binuclear enantiomers were doped into a room-temperature nematic liquid crystal, N-methoxybenzylidene-4-n-butylaniline. Helical twisting power (beta(M)) was found to be +97.9 and -88.9 mu m(-1) for Lambda Lambda- and Delta Delta-[Cr(acac)(2)(taet)Cr(acac)(2)], respectively. The values were compared with beta(M) for the monomeric enantiomers (+99.5 and -91.0 mu m(-1) for Lambda- and Delta-[Cr(acac)(3)], respectively). The results are interpreted on the basis of the surface chirality model. Delta Delta-[Cr(acac)(2)(taet)Cr(acac)(2)] was found to photoisomerize both in a hexane solution and in a liquid crystal phase of ZLI-1132. The quantum yield of photoisomerization in a liquid crystal phase was lowered to ca. 30% of that in a hexane solution.

Geiser, U. and H. U. Guedel (1981). "Single-crystal circular dichroism of [(+)D-Cr(en)3]3+." Inorganic Chemistry 20(9): 3013-3019.
	
Hannon, M. J., et al. (2001). "Paper: a cheap yet effective chiral stationary phase for chromatographic resolution of metallo-supramolecular helicates." Chemical Communications(12): 1078-1079.
	Simple paper chromatography using brine as an eluent affords the two enantiomers of metallo-supramolecular triple-helicates. The technique may be scaled up for preparative resolution by using cellulose columns in conventional column chromatography.

Herren, M., et al. (1996). "Photoluminescence of Enantio-Selectively Formed Chromium(III) Double Salts." Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals 285: 573-578.
	
Hilmes, G. L., et al. (1977). "Optical activity of the 4A2 .tautm. 2E transition in chromium(en)33+." Inorganic Chemistry 16(3): 528-533.
	
Jia, J., et al. (2016). "Theoretical Analysis on the Importance of Achiral Unidentate Ligands to Electronic Circular Dichroism of cis-Bis(ethylenediamine) Cobalt(III) Complexes." Inorganic Chemistry 55(14): 6949-6960.
	
Jimenez, J. R., et al. (2019). "Chiral Molecular Ruby [Cr(dqp)2](3+) with Long-Lived Circularly Polarized Luminescence." J Am Chem Soc 141(33): 13244-13252.
	The chiral resolution of a kinetically inert molecular ruby [Cr(dqp)2](3+) (1, dqp = 2,6-di(quinolin-8-yl)pyridine) displaying strong dual light emission at room temperature has been achieved. The wrapped arrangement of the six-membered dqp chelating ligands around the Cr(III) provided nonplanar helical conformations leading to the diastereoselective assembly of chiral bis-tridentate monometallic Cr(III)-helix. The PP-(+)-[Cr(dqp)2](3+) and MM-(-)-[Cr(dqp)2](3+) enantiomers could be separated and isolated by using cation-exchange chromatography and subsequent salt-metathesis with KPF6. X-ray crystallographic analysis based on Flack parameters assigned the absolute configurations of the two enantiomers. Circularly polarized luminescence (CPL) spectra showed two polarized emission bands within the NIR region corresponding to the characteristic metal-centered spin-flip Cr((2)E --> (4)A2) and Cr((2)T1 --> (4)A2) transitions with exceptionally high dissymmetry factors, |glum|, of 0.2 and 0.1, respectively, which are comparable to those reported for rare-earth chiral complexes. Photophysical properties also revealed an extremely long excited-state lifetime of 1.2 ms and a high quantum yield of 5.2% at room temperature in water. These properties make [Cr(dqp)2](3+) an ideal sensitizer for the preparation of enantiopure luminescent supramolecular energy-converting devices and also open up the possibility of using chiral Cr(III) chromophores for the construction of NIR-CPL materials and polarized photonic devices based on earth-abundant metals.

Jiménez, J.-R., et al. (2021). "Bright Long-Lived Circularly Polarized Luminescence in Chiral Chromium(III) Complexes." Angewandte Chemie International Edition 60(2).
	Two wrapped right hands are required for building “La Cathédrale” by Auguste Rodin. Two right-handed helical ligands are necessary for designing CPL emissive ruby-type complexes as reported by Juan-Ramón Jiménez, Claude Piguet et al. in their Research Article (DOI: 10.1002/anie.202101158).

Kaizaki, S. (2012). Applications of Electronic Circular Dichroism to Inorganic Stereochemistry. Comprehensive Chiroptical Spectroscopy: 449-471.
	Summary This chapter contains sections titled: Introduction ECD in the D-D Transitions of Tris- or BIS-Bidentate Transition Metal Complexes Polynuclear Complexes with Configurational Chirality ECD in the 4f -4f Transitions Exciton ECD in the Intraligand Transitions Atropisomerism and ECD Summary References

Kaizaki, S., et al. (1969). "Circular Dichroism of Chromium(III) Complexes. I. L-Tartrato Complexes. Their Stereospecific Formation and Spin-forbidden Absorption Bands." Bulletin of the Chemical Society of Japan 42(4): 988-994.
	Two novel mixed chromium (III) complexes containing L-tartrates and 2,2′-dipyridyl or 1,10-phenanthroline have been prepared, and their electronic absorption and circular dichroism spectra and the rotatory dispersion have been measured in the region of near-infrared to ultraviolet. From the construction of molecular models and from the comparison of the CD bands of the present complexes with those of the resolved oxalato complexes, (−)546-K[Cr(ox)2(dip)]·3H2O and (−)546-K[Cr(ox)2(phen)]·4H2O, it has been concluded that the present complexes have a binuclear structure in which two Cr(III) ions are bridged by two tetradentate L-tartrato ligands and that the absolute configuration of the binuclear complexes is Λ(C2)-Λ(C2). Their formation is completely stereospecific and their formulae are represented by Ba[Cr2(L-tart2H)(dip)2]2·9H2O and NH4[Cr2(L-tart2H)(phen)2]·6.5H2O. The absolute configurations of several complexes which commonly belong to a general type, cis-[Cr(O)4(N)2] have been determined on the basis of circular dichroism studies of the present binuclear complexes. The circular dichroism in the spin-forbidden absorption band region have also been measured and discussed.

Kaizaki, S., et al. (1970). "Circular Dichroism of Chromium(III) Complexes. II. Correlation between Behavior in the Spin-forbidden Absorption Band Region and Absolute Configurations." Bulletin of the Chemical Society of Japan 43(4): 1100-1109.
	The absorption and circular dichroism (CD) spectra of twelve optically active chromium (III) complexes containing three bidentate ligands have been measured in the near-infrared to ultraviolet region. CD spectra in the spin-forbidden d-d absorption band region have been considered mainly in relation to the CD bands in the first spin-allowed d-d absorption band region. It has been concluded that the absolute configurations of chromium (III) complexes can be determined on the basis of the signs of the CD bands in the spin-forbidden band region. The splitting components of the CD bands in the spin-forbidden band region have been discussed considering the crystal field treatment by Macfarlane.

Kaizaki, S., et al. (1970). "Exciton Circular Dichroism of Chromium(III) Complexes Containing Two Nonidentical α-Diimines." Bulletin of the Chemical Society of Japan 43(9): 3024-3024.
	
Kaizaki, S., et al. (1973). "Circular dichroism of chromium(III) complexes. IV. Elucidation of circular dichroism in the spin-forbidden transitions." Inorganic Chemistry 12(1): 142-150.
	
Kaizaki, S., et al. (1975). "Preparation of cis- and trans-Dicyanobis(ethylenediamine)chromium(III) Complexes and Optical Resolution of the cis Isomer." Bulletin of the Chemical Society of Japan 48(3): 902-905.
	Two geometrical isomers, cis and trans, of [Cr(CN)2(en)2]+ were prepared and the cis isomer was resolved into optical isomers. The ligand field absorption and circular dichroism spectra were discussed and the absolute configuration of cis-(+)546-[Cr(CN)2(en)2]+ was determined to Λ on the basis of the circular dichroism sign in the first spin-allowed d-d band region.

Kaizaki, S. and M. Ito (1981). "Circular Dichroism of Chromium(III) Complexes. VI. Preparation, Optical Resolution, and Circular Dichroism Spectra of (Amino acidato)bis(ethylenediamine)chromium(III) Complexes." Bulletin of the Chemical Society of Japan 54(8): 2499-2502.
	Three (amino acidato)bis(ethylenediamine)chromium(III) complexes were prepared and resolved into their optically active isomers, their absorption and circular dichroism spectra being measured in the spin-forbidden and spin-allowed d-d transition regions. The amino acids used were glycine, L-alanine, and L-phenylalanine, the latter two yielding pairs of diastereomeric, not enantiomeric, isomers in their complexes. The configurational and vicinal CD curves were obtained from the observed CD of each pair of diastereomers. The additivity of configurational and vicinal contributions to the optical activity in the whole region of the d-d transitions was substantiated. The configurational and vicinal CD peaks in the spin-forbidden band region were assigned in connection with those in the first spin-allowed band region.

Kaizaki, S., et al. (1985). "Circular-Dichroism of Chromium(Iii) Complexes .10. Circular-Dichroism Spectra in the Spin-Forbidden Transitions of Criii(N)6 Type Complexes with Chiral Diamines." Inorganic Chemistry 24(13): 2080-2088.
	
Kaizaki, S. and H. Mori (1981). "Circular Dichroism of Chromium(III) Complexes. VII. Circular Dichroism in the Spin-forbidden Transitions of cis-[Cr(N2)(O)4] Type Complexes with Ethylenediaminetetraacetate Analogues." Bulletin of the Chemical Society of Japan 54(11): 3562-3565.
	Potassium (2S,4S)-2,4-pentanediaminetetraacetatochromate(III) monohydrate was newly prepared and was found to be formed stereospecifically with a Λ(ΛΔΛ) absolute configuration as has been revealed for the corresponding Co(III) complex. The circular dichroism spectra in the spin-forbidden transitions of this new complex along with the known analogues, (−)589-ethylenediamine-N,N′-diacetato-N,N′-dipropionatochromate(III) and (+)589-(S,S)-2,2′-(ethylenediimino)disuccinatochromate(III) complexes, were measured and discussed in comparison with those in the first spin-allowed transitions on the basis of the theoretical relations between the rotational strengths for the spin-forbidden and the spin-allowed transitions in trigonal and tetragonal fields.

Kaizaki, S. and Y. Shimura (1977). "Circular Dichroism of d-d Transitions of Cr (III) and Co (III) Complexes." Journal of the Spectroscopical Society of Japan 26(3): 127-147.
	
Kalf, I., et al. (2002). "Chiral Cr(III) and Co(III) complex cations as building blocks for ordered and disordered salts." Crystengcomm 4: 548-551.
	Cobalt and chromium compounds of the composition [M(chxn)(3)]Cl-3 (chxn = trans-1,2-diaminocyclohexane) have been used as building blocks to synthesize ternary salts. Chirality of the cations allows control of the nature of the products. Joint crystallisation of Co(III) and Cr(III) complexes of the same configuration, i.e. both derived from either the same enantiomer or the racemate of the chiral chelating ligand, results in either homochiral or heterochiral solid solutions. Complex salts [M(rac-chxn)(3)]Cl-3.H2O(M = Co, Cr) crystallise in the tetragonal racemic space group I (4) over bar 2d. The preferred formation of this heterochiral structure offers the oppurtunity to synthesize an ordered solid of predictable geometry via the quasi-racemate approach: when Co( III) and Cr( III) cationic complexes of opposite chirality are cocrystallised, no solid solutions but a well-ordered ternary salt is obtained. X-Ray diffraction reveals a t(2) group subgroup relationship between the racemic parent structure and the mixed crystals. The latter crystallise in the orthorhombic space group I2(1)2(1)2(1) with lattice parameters reflecting the different size requirements of trivalent cobalt and chromium cations.

Kane-Maguire, N. A. P. and J. F. Wheeler (2001). "Photoredox behavior and chiral discrimination of DNA bound M(diimine)(3)(n+) complexes (M = Ru2+, Cr3+)." Coordination Chemistry Reviews 211: 145-162.
	An overview is given of the rapidly developing field of bioinorganic chemistry involving the interaction of Ru(diimine)(3)(2+) complexes with double-stranded DNA. This contribution focusses on the photoredox behavior of these DNA bound systems and the presence of chiral discrimination in the binding process. Cr(diimine)(3)(3+) complexes are attractive new candidates for such studies in view of their long-lived room temperature luminescence and strong excited state oxidizing power. For these Cr(III) systems we observe strong quenching of the emission signal in the presence of B-DNA, and provide evidence that this quenching is associated with a photoredox process involving guanine base oxidation. We also demonstrate the value of capillary electrophoresis (CE) as a technique for assessing the relative binding constants and the stereoselectivities of transition metal interactions with DNA. In addition, we explore the use of CE as an alternative approach to help resolve literature disagreements between different Ru(phen)(3)(2+)/DNA binding models. (C) 2001 Elsevier Science B.V. All rights reserved.

Konrad, F., et al. (2009). "Bis(oxazolinylmethyl) Derivatives C4H4E Heterocycles (E = NH, O, S) as C-2-Chiral Meridionally Coordinating Ligands for Nickel and Chromium." European Journal of Inorganic Chemistry(33): 4950-4961.
	The synthesis of the three ligands employed in this study is based on the condensation of two molar equivalents of (S)valinol with the diester precursors pyrrole-2,5-bis(ethyl)acetate (2a), furan-2,5-bis(ethyl)acetate (2b) and thiophene-2,5-bis (ethyl) acetate (2c). This gave the corresponding bis(oxazolinyhnethyl)pyrrole (iPrL(O), 4a), bis(oxazolinylmethyl)furan (iPrL(O), 4b) and bis(oxazolinylmethyl)thiophene (iPrL(S), 4c) ligands. Stirring 4a in MeOD at ambient temperature in the presence of a catalytic amount of acetic acid (1 mol-%) led to complete hydrogen/deuterium exchange in the two bridging methylene groups of the ligand. This behaviour is explained by an acetate-mediated reversible proton transfer between the oxazoline N atom and the methylene bridge, a conjecture which was supported by a DFT study of the process. Deprotonation of iPrL(N)H (4a) with tBuLi at -78 degrees C and subsequent stirring with NiCl2 yielded the square planar nickel(II) complex [Ni(iPrL(N))Cl] (5). However, on stirring iPrL(N)H (4a) with nickel acetate in methanol, a deep red nickel acetato complex [Ni(iso-iPrL(N))(OAc)] (6) bearing the isomerized tridentate pincer ligand was obtained. Reaction of acetato complex 6 with Me3SiCl in dichloromethane cleanly gave the corresponding chlorido complex [Ni(iso-PrLN)Cl] (7), which is the isomer of compound 5. The intra-ligand rearrangement was explained by acetate-mediated proton transfer between the methylene bridges and the 3/4-positions of the pyrrole ring, the computed thermodynamic driving force being Delta G = -9.8 kcalmol(-1). Neither thiophene derivative 4c nor furan-derived ligand 4b gave robust, isolable complexes with nickel(II). However, reaction of iPrL(O) (4b) with [CrCl3(thf)(3)] in thf yielded the yellow-green complex [CrCl3(iPrL(O))] (8), whereas no complexation occurred with the analogous thiophene-derived bisoxazolme 4c. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Kuroda, R. and P. Biscarini (1990). "Chiral Discriminations of Complexes with D3 Symmetry - Molecular-Structure and Crystal-Packing Mode of (-)589-Tris[(-)-O,O'-1(R),2(R)-Dimethylethylene Dithiophosphato]Chromium(Iii), [Cr((-)Bdtp)3]." Journal of the Chemical Society-Dalton Transactions(11): 3393-3397.
	
Lin, I. and D. Dunawaymariano (1988). "Synthesis and Stereochemical Analysis of Exchange-Inert Chromium(Iii) Complexes of Adenosine 5'-O-(2-Thiodiphosphate), Adenosine 5'-O-(2-Thiotriphosphate), and Adenosine 5'-O-(3-Thiotriphosphate) - Generation of a New Class of Chiral Enzyme Active-Site Probes." Journal of the American Chemical Society 110(3): 950-956.
	
Madaras, J. S. and H. G. Brittain (1980). "Induced optical activity in the terbium(III) complex of pyridine-2,6-dicarboxylic acid through association with resolved tris(ethylenediamine)chromium(III)." Inorganic Chemistry 19(12): 3841-3842.
	
Malisch, W., et al. (1993). "Phosphenium Complexes of the Chromium and Iron-Group - Novel Cycloaddition Reactions and the Chemistry of Ph-Functional and Chiral Derivatives." Phosphorus Sulfur and Silicon and the Related Elements 77(1-4): 569-572.
	Synthesis of the highly reactive phosphenium complexes C5R5(CO)2M-P(H)R' (R = H, Me; R' = t-Bu, Mes, s-Mes) (2a - d) is described. The mesityl derivative shows spontaneous dimerization to give the dinuclear species C5R5(CO)2W=P(Mes)-W(CO)(PH2Mes)C5R5 (6a, b), a new type of phosphinidene complex. An alternative access to these species involves deprotonation and decarbonylation of the bis(metallo)phosphonium salts {[CP(CO)2W]2P(Mes)H}BF4 (9a, b). Cycloaddition reaction of the phosphenium complexes Cp(CO)(HPh2P)M=PPh2 (MO, W) (16a, b) and Cp(CO)Fe=PMes2 (18a, b) respectively with   isothiocyanates     yields   novel     fourmembered phosphametallacycles L(n)M-PR2-C(NR')-S (R-=Et,       t-Bu) (17a, b, 18a, b).

Manson, N. B. and G. A. Shah (1977). "Coupling of T1u and T2u vibrations to the 2Eg to 4A2g transition in MgO:V2+ and MgO:Cr3+." J. Phys. C Solid State Phys. 10(11): 1991–2003.
	
McCaffery, A. J., et al. (1969). "Optical rotatory power of co-ordination compounds. Part XII. Spectroscopic and configurational assignments for the tris-bipyridyl and -phenanthroline complexes of the di- and tri-valent iron-group metal ions." Journal of the Chemical Society A: Inorganic, Physical, Theoretical(0): 1428-1441.
	Absorption and circular dichroism spectra are reported for the tris-bipyridyl and the -phenanthroline (phen) complexes of iron(), ruthenium-() and -(), and osmium-() and -(). The results are analysed in terms of the exciton model for optical activity and the perturbing effects of -electron exchange between the ligands and between the ligands and the metal ion. It is found that the principal spectroscopic and stereochemical conclusions of the exciton theory are qualitatively unaffected by the perturbations, provided that the complete monopole exciton energy is considered rather than that evaluated in the point-dipole approximation. Metal–ligand -bonding is shown to be more important in the di- than the tri-valent complexes, the apparent exciton-splitting being diminshed in both cases. Ligand–ligand bonding may enhance or decrease the exciton splitting, depending upon the symmetry of the ligand -orbitals with respect to rotation about the two-fold (short) ligand axis. The -band in the spectra of bipyridyl and phenanthroline is found to be predominantly long-axis polarised, although there is a short-axis component in the latter case due to the overlapping -band. The higher energy β-band is shown to be short-axis polarised in both cases. The main circular dichroism of the complexes in the visible region is found to reflect the exciton dichroism of the u.v. region, owing to the combination of long-axis polarised charge-transfer transitions with ligand excitations of the same polarisation. The optical isomers studied are assigned the () stereochemical configuration established for (–)-[Fe phen] by -ray analysis.

Minor, S. S. and G. W. Everett (1976). "Thermal-Isomerization and Photoisomerization of a Chiral Chromium(Iii)-Beta-Diketone Complex in Normal-Hexane Solution." Inorganic Chemistry 15(7): 1526-1530.
	
Miyoshi, K., et al. (1982). "Inversion in the Direction of a Chiral Equilibrium Shift Observed in the Pfeiffer Effect of Some Mixed-Chelate Chromium(Iii) Complexes at the Ligand-Field Excited-State." Inorganic Chemistry 21(2): 790-793.
	
Morita, M., et al. (1984). "Circularly Polarized Luminescence of (-)D-[Cr(R-Pn)3]3+ and Related Chiral Chromium(Iii) Complexes Using a Microcomputer-Based Digital Spectrophotometer System." Journal of Luminescence 31-2(Dec): 558-560.
	
Nagata, Y. and T. Mori (2020). "Irreverent Nature of Dissymmetry Factor and Quantum Yield in Circularly Polarized Luminescence of Small Organic Molecules." Frontiers in Chemistry 8(448).
	Recently, a rational modification of small organic molecules has attracted considerable attention for designing advanced materials with enhanced circularly polarized luminescence (CPL) activity. A particular emphasis has been placed on fully allowed π-π<sup>*</sup> transition of rigid aromatic systems, due to their relatively superior emission properties or quantum yields of luminescence (Φ<sub>lum</sub>). However, their dissymmetry factors (g<sub>lum</sub>), differential left and right CPL intensities, are typically disappointingly low at least in one to two orders of magnitude. Truly useful organic CPL materials, rated by a circular polarization luminosity index (Λ<sub>CPL</sub>) per single molecule, possess both |g<sub>lum</sub>| and Φ<sub>lum</sub> values high. However, how to improve these two factors simultaneously with a proper molecular design is an open question. Here, we addressed this issue by theoretical and statistical inspection on a possible relation of the g<sub>lum</sub> and Φ<sub>lum</sub> values. According to the analysis, we propose simple, unpretentious, yet pertinent guidelines for designing superior organic CPL materials for the future with large Λ<sub>CPL</sub> values.

Otto, S., et al. (2015). "[Cr(ddpd)2]3+: A molecular, water-soluble, highly NIR-emisssive Ruby analogue." Angew. Chem. Int. Ed. 54(39): 11572-11576.
	
Peacock, R. D. and B. Stewart (1982). "Circular dichroism of transition metal complexes." Coordination Chemistry Reviews 46: 129-157.
	
Peacock, R. D. and B. Stewart (1982). "The circularly polarised luminescence spectrum of [Cr(en)3]3+ in the uniaxial single crystal host 2[Rh(en)3Cl3].NaCl.6H2O." Journal of the Chemical Society, Chemical Communications(5): 295-296.
	The circularly polarised luminescence spectrum of a transition metal ion complex in a uniaxial single crystal host has been measured for the first time; individual vibronic lines of the [Cr(en)](en = ethylenediamine) emission spectrum were found to be circularly polarised and two distinct chiral emitting species were detected.

Radanović, D. J., et al. (1991). "Circular dichroism of chromium(III) hexadentate edta-type complexes Part III. Ethylenediamine-N-acetato-N,N′,N′-tri-3-propionatochromate(III) ion." Inorganica Chimica Acta 186(1): 13-19.
	A new hexadentate chromium(III) complex with ethylenediamine-N-acetic-N,N′,N′-tri-3-propionic acid [H4eda3p) is reported. Only one (trans(O5O6)) geometrical isomer of the [Cr(eda3p)]− complex ion was prepared and resolved into optical isomers. IR, electronic absorption and CD spectra were used for characterizing the complex. CD data in the region of the d-d transitions are discussed in comparison with those of other edta-type Cr(III) complexes of known configuration. The (−)589-isomer of the trans(O5O6)-[Cr(eda3p)]− complex, having a positive CD peak at lowest energy in the first spin-allowed d-d absorption band region, is tentatively assigned the Λ configuration.

Radanovic, D. J. and B. E. Douglas (1975). "CIRCULAR DICHROISM OF CHROMIUM(III) SEXADENTATE EDTA-TYPE COMPLEXES, PART I (S, S)-Ethylenediamine-N, N'-disuccinatochromate(III) and Ethylenediamine-N, N '-Diacetato-N, N'-Di-3-Propionatochromate(III) Ions." Journal of Coordination Chemistry 4(3): 191-198.
	
Rapenne, G., et al. (1999). "Resolution, X-ray structure and absolute configuration of a double-stranded helical diiron(II) bis(terpyridine) complex." Chemical Communications(18): 1853-1854.
	A dinuclear double helix constructed around two iron() bis(terpyridine) centres has been resolved by preparative column chromatography, several tens of milligrams of each enantiomer were obtained, with an excellent enantiomeric excess.

Riehl, J. P. and S. Kaizaki (2010). Phys. Inorg. Chem. Princ. Methods, Model. : 143–197.
	
Sakabe, Y. and H. Ogura (1991). "CIRCULAR-DICHROISM STUDIES FOR ABSOLUTE-CONFIGURATION DETERMINATION OF 1,2-DIAMINOPROPANE CHROMIUM(III) COMPLEXES, AND SYNTHESIS OF TETRACYANO(1,2-DIAMINOPROPANE)CHROMATE(III)." Inorganica Chimica Acta 189(2): 225-228.
	This is the first study of the absolute configuration determinations for metal complexes coordinated by chiral propylenediamine ligands, using CD spectra. The CD (circular dichroism) spectra of analogous Cr(III) complexes represented by [Cr(CN)2n(A)3-n]3-2n (A = pn or en, n = 0 or 1, pn = d-pn or l-pn and pn = 1,2-diaminopropane = propylenediamine, en = ethylenediamine) have been systematically measured, and they have been compared with that of the LAMBDA-cis-(-)589-[Cr(CN)2(d-pn)2]Cl standard, of which an absolute configuration has been confirmed by X-ray analysis, and absolute configurations of the seven complexes have been collectively determined. In this study the two new complexes of tetracyano(d- or l-1,2-diaminopropane)chromate(III) are synthesized to learn the contribution of the chiral configurations, localized upon the propylenediamine ligands, to CD spectra of complexes, because CD peaks, depending on the chiral propylenediamine, are liable to interfere with correct absolute configuration determinations. We have elucidated the effectiveness of using CD spectra as the absolute configuration determination method. The superiority of this method is particularly obvious when complexes cannot answer to X-ray analysis-as was the case with several complexes in this study-due to the difficulty in preparing single crystals.

Schellman, J. A. (1975). "Circular dichroism and optical rotation." Chemical Reviews 75(3): 323-331.
	
Seyler, K. L., et al. (2018). "Ligand-field helical luminescence in a 2D ferromagnetic insulator." Nature Physics 14(3): 277-281.
	Bulk chromium tri-iodide (CrI3) has long been known as a layered van der Waals ferromagnet1. However, its monolayer form was only recently isolated and confirmed to be a truly two-dimensional (2D) ferromagnet2, providing a new platform for investigating light–matter interactions and magneto-optical phenomena in the atomically thin limit. Here, we report spontaneous circularly polarized photoluminescence in monolayer CrI3 under linearly polarized excitation, with helicity determined by the monolayer magnetization direction. In contrast, the bilayer CrI3 photoluminescence exhibits vanishing circular polarization, supporting the recently uncovered anomalous antiferromagnetic interlayer coupling in CrI3 bilayers2. Distinct from the Wannier–Mott excitons that dominate the optical response in well-known 2D van der Waals semiconductors3, our absorption and layer-dependent photoluminescence measurements reveal the importance of ligand-field and charge-transfer transitions to the optoelectronic response of atomically thin CrI3. We attribute the photoluminescence to a parity-forbidden d–d transition characteristic of Cr3+ complexes, which displays broad linewidth due to strong vibronic coupling and thickness-independent peak energy due to its localized molecular orbital nature.

Telfer, S. G., et al. (2004). "CD spectra of d-f heterobimetallic helicates with segmental di-imine ligands." Inorg. Chem. 43: 5302-5310.
	
Tsubomura, T., et al. (1988). "Luminescence of chronium(III) l-alaninato and other related complexes." Journal of Luminescence 40-41: 268-269.
	Luminescence and circularly polarized luminescence of both the monomeric and dimeric chiral chronium alaninato complexes were studied to investigate the electonic states and the optical activity.

Tsubomura, T., et al. (1991). "Luminescence and Circularly Polarized Luminescence of Mononuclear and Binuclear Chromium(III) L-Alaninato Complexes." Bulletin of the Chemical Society of Japan 64(8): 2341-2348.
	Luminescence and circularly polarized luminescence (CPL) spectra were investigated at low temperatures in order to clarify the chiroptical and electronic structures of monomeric and dimeric chromium(III) alaninato complexes. In the monomeric complexes, [Cr(L-(or D-)ala)3]·H2O, R1 and R2 lines of opposite spectral signs were found in the CPL spectra. The signs and relative intensities of the peaks were found to be comparable with circular dichroism (CD) spectra by employing theoretical arguments based on a strong crystal field theory. In the case of hydroxo-bridged dimeric complexes, [Cr2(OH)2(L-(or D-)ala)4]·3H2O, although the luminescence spectra of exchange-coupled pair states were clearly observed with a deduction of reasonable exchange interaction parameters, the CPL spectral components were not discernible because of the meso-type structure.

Vijayalakshmi, R., et al. (2006). "Interaction of chromium(III) complex of chiral binaphthyl tetradentate ligand with DNA." Bioorganic & Medicinal Chemistry 14(10): 3300-3306.
	Since conformation of the molecule plays a vital role in the activity of drug, we have investigated the DNA interaction of a chromium(III) complex with ligands in two conformations. Chromium(III) complexes derived from chiral binaphthyl Schiff base ligands, viz. R- and S-2,2'-bis(salicylidencamino) 1,1'-binaphthyl, have been synthesized and characterized by mass, IR, and electronic spectra. The interaction of these R- and S-binaphthyl Schiff base chromium(III) complexes with CT-DNA was investigated with the goal of examining whether the chirality has an influence on the chromium(III)-DNA binding properties. The difference in chirality of the ligand did not show any striking difference in binding properties. The binding constants for R and S conformers were estimated to be 18 (+/- 0.4) x 10(3) and 9.4 (+/- 0.3) x 10(3) M-1, respectively, through spectroscopic titrations. All the experimental results are suggestive that both the isomers are DNA groove binders. The results of steady-state as well as time-resolved fluorescence experiments, however, suggest that the R conformer has restricted mobility when bound to DNA because it is more deeply buried in the groove of DNA compared to the S isomer. (c) 2006 Elsevier Ltd. All rights reserved.

Yamaga, M., et al. (1990). "Polarized photoluminescence from Cr3+ ions in laser host crystals III. ZnWO4." Journal of Luminescence 47(1): 65-70.
	We report the temperature dependence and polarization properties of the zero-phonon lines and broad band emission of the 4T2 → 4A2 emission of Cr3+ ions substituting for Zn2+ ions in ZnWO4. The zero-field splitting of the 4T2 state is calculated and compared to the separation of the zero-phonon lines associated with this broad emission band. A molecular orbital (MO) method is used to calculate the polarization properties of the emission. Comparison with experiment suggests that T2u odd-parity distortion and odd-mode vibrations are most effective in inducing the broad band transition.

Yamamoto, Y. and Y. Shimura (1981). "Metal-Complexes Coordinating Pyridine-Derivatives .3. Stereoselective Formation of Chromium(Iii) Complexes of Chiral Quadridentate Ligands." Bulletin of the Chemical Society of Japan 54(10): 2934-2929.
	
