Synthesis of Boron(III)-Coordinated Subchlorophins and Their Peripheral Modifications.

Abstract

A pyrrole-cleaving modification to transform boron(III) meso-triphenylsubporphyrin into boron(III) meso-triphenylsubchlorophin has been developed. Boron(III) subchlorophins thus synthesized show absorption and fluorescence spectra that are roughly similar to those of boron(III) subchlorins, but B-methoxy boron(III) subchlorophin showed considerably intensified fluorescence and a small Stokes shift. Peripheral modification reactions of B-phenyl boron(III) subchlorophin such as regioselective nitration with Cu(NO3 )2 ⋅3 H2 O, ipso-substitution reactions of boron(III) α-nitrosubchlorophin with CsF and CsCl, and Pd-catalyzed cross-coupling reactions of boron(III) α-chlorosubchlorophin with arylacetylenes, have been also explored to tune the optical properties of subchlorophins.