Effects of interaction between the chelate rings and π‐conjugated systems in fused salphen complexes on UV‐Vis‐NIR spectra

Abstract

Dinuclear (Zn 2 , Ni 2 , and NiZn) complexes of fused salphen with acene-type annelation were synthesized from 3,7-diformyl-2,6-dihydroxynaphthalene. The spectroscopic properties of these complexes were compared with those of their constitutional isomers with phene-type annelation. The acene-type complexes exhibited a characteristic absorption band in the near-infrared region that showed a noticeable solvent effect. Time-dependent density functional theory calculations suggested that the absorption arose from a π ! π* transition localized at the naphthalene ring, which was perturbed by the adjoining chelate rings. Effects of the connection topology in the fused salphen complexes are discussed by comparison with those of polycyclic aromatic hydrocarbons.

Cationic Co–Salphen Complexes Bisligated by DMAP as Catalysts for the Copolymerization of Cyclohexene Oxide with Phthalic Anhydride or Carbon Dioxide

“…Highly active dinuclear Co­(III) complexes reported by Lu had a 7.7–7.9 Å metal–metal distance . In sharp contrast to these reported examples, the Co–Co distances in complexes 5 and 6 were estimated to be 10.3 and 10.8 Å, respectively, based on DFT calculations of their Ni analogues . The distances are much longer than any of the precedents, implying that the observed “bimetallic effect” for complex 5 could be different from the simple fixation of the two metal centers at the appropriate distance: Electronic interaction between the two metal centers might have contributed to the improved catalytic activities of 5 in both reactions.…”

“…24 In sharp contrast to these reported examples, the Co− Co distances in complexes 5 and 6 were estimated to be 10.3 and 10.8 Å, respectively, based on DFT calculations of their Ni analogues. 25 The distances are much longer than any of the precedents, implying that the observed "bimetallic effect" for complex 5 could be different from the simple fixation of the two metal centers at the appropriate distance: Electronic interaction between the two metal centers might have contributed to the improved catalytic activities of 5 in both reactions. On the other hand, the catalytic activity for CHO/PA copolymerization with bimetallic 5 increased under higher dilution (entries 3 and 9, Table 1), being contrastive to the slight drop of activity with monometallic 3 and 4 (entries 1, 2 and 7, 8).…”