Programmed Metalloporphyrins for Self-Assembly within Light-Harvesting Stacks: (5,15-Dicyano-10,20-bis(3,5-di-tert-butylphenyl)porphyrinato)zinc(II) and Its Push−Pull 15-N,N-Dialkylamino-5-cyano Congeners Obtained by a Facile Direct Amination
摘要:
The title dicyano compound was synthesized via cyanation and it self-assembles in nonpolu solvents giving red-shifted and broad absorption maxima just as the bacteriochlorophylls which are encountered in the lightharvesting organelles of early photosynthetic bacteria. In the crystal, stacks are formed through a hierarchic combination of.7r-stacking and a CN-Zn electrostatic interaction. Push-pull 15-NN-dialkylamino-5-cyano congeners could be obtained in high yields using a solvent- and catalyst-free direct amination of mesobromoporphyrins. Importantly, the fluorescence of the self-assembled species due to the very orderly manner in which the chromophores are arranged is not entirely quenched and has a surprisingly long lifetime of over 1 ns. This lends hope of using the trapped energy in biornimetic hybrid solar cells.