Two zinc-viologen interpenetrating frameworks with straight and offset stacking modes respectively showing different photo/thermal responsive characters

Two photo/thermal responsing donor-acceptor molecular systems have been designed and synthesized based on the interpenetrating metal organic frameworks (MOFs). For compound 1 [Zn(CPBPY)(HBTC)]•H2O, the formation of four-fold interpenetrating diamond structure displays reversible photochromic behavior upon light/heat stimuli with offset  stacking figure for the donor carboxylate and acceptor viologen units. By comparison, the two-fold parallel interpenetrating framework in compound 2 [Zn2(CPBPY)2(BTEC)]•2H2O•2CH3CH2OH exhibits photocoloration and thermalcoloration behaviors accompanying long-lived charge separation upon light/heat stimuli with face to face -stacking figure for the donor carboxylate and acceptor viologen units. Faster responsive rate and stable charge separation status is observed in the system of 2 due to its large π-conjugation molecular system formed by the sandwich type π–π stacking structure. This example of structure-controlled photoresponsive systems shows a way to drive toward tun...