A series of 5,15-diphenylporphyrinatonickel(II) derivatives containing electron-releasing (Me(2)NC(6)H(4)C&tbd1;C-) and -withdrawing groups [-CHO, -CH=C(CN)(2), -CH=C(CO(2)Et)(2), -CH=CHCHO] in opposite meso positions has been synthesized through the classical formylation, halogenation, Knoevenagel condensation, and palladium-catalyzed cross-coupling reaction of porphyrins. The molecular first hyperpolarizabilities (beta) of two of these push-pull porphyrins, namely 5-(2',2'-dicyanoethenyl)-15-[[4"-(N,N-dimethylamino)phenyl]ethynyl]-10,20-diphenylporphyrinatonickel(II) (7) and 5-formyl-15-[[4'-(N,N-dimethylamino)phenyl]ethynyl]-10,20-diphenylporphyrinatonickel(II) (8) have been determined experimentally by electric-field-induced second-harmonic generation (EFISH) at 1907 nm and computationally by semiempirical methods (ZINDO sum-over-states). The values of beta(&mgr;) (124 and 66 x 10(-)(30) cm(5) esu(-)(1), for 7 and 8, respectively) are moderate because the acceptor group is significantly tilted with respect to the porphyrin core in these complexes, which decreases the electronic coupling across the system. This nonplanar geometry has been confirmed by X-ray structure analyses and molecular modeling studies.
The 1,3-dipolar cycloadditions of alkynyl Fischer carbene complexes with nitrones to give 2,3-dihydroisoxazole carbene complexes were found to undergo first-order kinetics both for the nitrones and alkynyl carbene complexes. The effects of metals, substitutents of the nitrones and complexes, and solvents were studied. The rates increased with the more electron rich nitrones and less electron rich metal complexes. Ab initio theoretical calculations supported that the HOMO of nitrones and the LUMO of carbene complexes were the interacting frontier molecular orbitals. Only little dependence of solvent was observed, and therefore a concerted pathway is more likely.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.