Solvatochromic or solvent dependent phenomena observed for transition metal complexes are analyzed in details from spectroscopic and stereochemical points of view. It is found that the solvation around the second coordination sphere in the metal complexes results in the bond length variation due to cis effect and/or trans influence leading to the spectroscopic and/or steric change and/or stereochemical flexibility of unidentate rotamer or chelate ring conformation.

Firstly, the ligand field absorption band components and solvent-dependent ²H NMR contact shifts of trans-and cis-[CrF₂(N)₄] type complexes with linear aliphatic tetraamines and aromatic imine ligands were found to be correlated with the acceptor numbers for solvents. The ligand field bands were examined by using the angular overlap model(AOM), and the solvatochromism could be ascribed to variations of the metal-ligand σ-bond interactions due to the selective solvation toward the axial fluoro ligands. The cis effect is found to provide a reasonable account for the solvent dependence of the spectroscopic observables for both the cis and trans complexes. The inverse correlation of the ²H NMR shifts for the 4- and 5- deuterons in the bpy complexes with the solvent electron acceptor number give direct evidence for the π-acceptor bond properties of aromatic imine ligands in the complexes. In addition, from the solvatochromism and solvent-dependent ²H NMR spectra of fac- [CrF₃(tpa)](tpa=tri-2-pyridylamine), the trigonal splitting in the first ligand field band as well as the high sensitivity of the Cr-py bond variation to solvation were revealed. The solvatochromism of the first ligand field absorption bands and/or the solvent dependence of ¹³C and ⁵⁹Co NMR shifts for trans- and cis- [M(N)₂(O)₄] type complexes of cobalt(III) or chromium(III) with various kinds of polyamine-N-polycarboxylato ligands could result from variations of the metal-ligand σ and/or π bond interactions due to the preferential solvation toward the oxygen p_π orbitals coplanar with the M(O)₂ coordinate planes in terms of the AOM parametrization.

Secondary, for the nitritochromium(III) complexes with optically active diamines, the conformational (rotational) isomerism of coordinated nitrito ligands will be discussed on the basis of the solvent-dependent CD spectra in the near-ultraviolet region of an intraligand absorption band localized on nitrito ligands. It is proposed that the CD variation in the intraligand transition region among the complexes concerned is responsible for the chiral arrangement of nitrito ligands.