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A new supramolecular chirogenic system on the basis of tetrakis(nickel porphyrin) and various enantiopure solvents, which was specifically designed for investigation of the chirogenic phenomenon upon extremely weak interaction modes and marginal chiroptical responses, is reported. The temperature was found to be a key factor controlling the chirality transfer process in these assemblies.

Irradiation of rac-[Ru(bpy)(2)(PhP(OMe)(2))(Cl)]Cl (2) at lambda > 460 nm results in the photochromic generation of a new atropisomer and chirality inversion, via rotation of the PhP(OMe)(2) moiety around the Ru-P bond. However, since the energetic barrier to rotation is low resulting in racemization, it was found that the formation of a supramolecular complex between 2 and gamma-cyclodextrin (gamma-CDx) facilitated the stabilization of the new atropisomeric conformation. On irradiation the bisignate signals in the circular dichroism spectrum of the 2:gamma-CDx complex were converted to an entirely new and distinct circular dichroism spectrum, as a result of a different spatial orientation of the phenyl electronic transition in the PhP(OMe)(2) moiety (the active circular dichroism spectra were found to arise from different g factor values of the Delta-2:gamma-CDx and Lambda-2:gamma-CDx complexes). The new atropisomer formation and subsequent thermally induced interconversion could be further detected by conventional and variable temperature (1)H NMR studies. Determination of the conformation of the new atropisomer was achieved by combining analysis of the changes in the circular dichroism spectra by exciton coupling theory with molecular modeling and DFT calculations.

The achiral syn conformer (face-to-face) of the ethane-bridged bis(zinc porphyrin) (syn-ZnD) transforms into the corresponding chiral extended anti bis-ligated species (anti-ZnD.L2) in the presence of enantiopure ligands (L: amino acid derivatives). The mechanism of the supramolecular chirality induction is based on chiral ligand binding to zinc porphyrins and subsequent formation of either right- or left-handed screw structures in anti-ZnD.L2. The screw structure formation arises from steric interactions between the bulkiest substituent at the asymmetric carbon of the ligand and the peripheral ethyl groups of the neighboring porphyrin ring directed towards the covalent bridge. The sign and amplitude of the induced circular dichroism (CD) are dependent on the steric bulk of the substituents at the chiral center. The greater difference in size between the chiral center's substituents gives the stronger induced CD signal. Rationalization of the ligand bulkiness effect on chirality induction by amino acid derivatives, application of this supramolecular system for the determination of ligand absolute configuration, and relative bulkiness of the substituents at the asymmetric carbon are discussed., (Copyright 2001 Wiley-Liss, Inc.)

The review deals with association of traffic accidents and visual state of drivers. The study in healthy professional drivers covered influence of visual defect patterns (short sight, lower visual acuity, unilateral amblyopia and single eye) on quality of car driving. The driving quality appeared to be influenced by factor causing lower visual acuity (changes in refraction and opacity of transparent eye structures). Binocular vision plays insignificant role in driving and maneuvering. Lower quality of maneuvering results mainly from diplopia, but not from loss of stereoscopic vision.