Single-crystal-to-single-crystal conversions of two metal-mediated photoreactive coordination polymers based on stereoselective [2+2] photocycloaddition reactions

Two photoreactive coordination polymers {[Zn(mu-OH2)(5-Me-1,3-bdc)(2,3'-bpe)]center dot H2O}(n) (1) and {[Ag-2(5-Me-1,3-Hbdc)(2,3'-bpe)(2)][Ag(5-Me-1,3-bdc)(2,3'-bpe)]center dot H2O}(n) (3) have been prepared based on the hydrothermal reactions between an asymmetrical olefin 1-(2-pyridyl)-2-(3-pyridyl)-ethylene (2,3'-bpe) and an auxiliary ligand 5-methyl-1,3-benzenedicarboxylic acid (5-Me-1,3-H(2)bdc) in the presence of Zn(NO3)(2)center dot 6H(2)O and AgNO3, respectively. UV irradiation of these two photoreactive compounds 1 and 3 resulted in the formation of two new coordination polymers {[Zn(mu-OH2)(5-Me-1,3-bdc)(HT-bpbpcb)(0.5)]center dot H2O}(n) (2, HT-bpbpcb = 1,3-bis(2-pyridyl)-2,4-bis(3-pyridyl)cyclobutane) and {[Ag-2(5-Me-1,3-Hbdc)(HH-bpbpcb)][Ag(5-Me-1,3-bdc)(2,3'-bpe)]center dot H2O}(n) (4, HH-bpbpcb = 1,2-bis(2-pyridyl)-3,4-bis(3-pyridyl)cyclobutane) based on stereoselective [2 + 2] photodimerization reactions through single-crystal-to-single-crystal conversions. These two photoreactions were further confirmed by H-1 NMR spectroscopy and powder X-ray diffraction.