Tetraolefin stereospecific photodimerization and photopolymerization in coordination polymers

In the context of the highly desirable design and preparation of smart materials with adjustable properties based on photoreactive compounds, we report two unique photoreactive coordination polymers (CPs),{[Zn(4-Iba) 2 (4-tkpvb)]·H 2 O} n (1 , 4-HIba = 4-iodobenzoic acid, 4-tkpvb = 1,2,4,5-tetrakis(4-pyridylvinyl)benzene) and [Cd(1,4-bdc)(4-tkpvb)] n ( 2 , 1,4-H 2 bdc = 1,4-benze-nedicarboxylic acid). Depending on the metal ions and auxiliary carboxylate ligands used, the 4-tkpvb ligands in 1 and 2 adopt different mutual arrangements, which facilitate the photodimerization and photopolymerization reactions in single crystal to single crystal (SCSC) transformations. Upon UV light irradiation which results in the dimerization of the 4-tkpvb ligands, the one-dimensional (1D) zigzag chainsof 1 are transformed into a two-dimensional (2D) network of {[Zn(4-Iba) 2 (bpbtpvcb) 0.5 ]·H 2 O} n ( 1a , bpbtpvcb = 1,3-bis(4-pyridyl)-2,4-bis(2,4,5-tri(2-(4-pyridyl)vinyl) phenylcyclobutane). Similarly, in the crystals of 2 , all 4-tkpvb ligands experience a photopolymerization reaction to form an unprecedented 1D linear organic polymer, poly-1,3-bis(4-pyridyl)-2,5-bis(2-(4-pyridyl)-vinyl) phenyl)cyclobutane (poly-bpbpvpcb). Furthermore, the 2D network of 2 is converted into a three-dimensional (3D) framework of [Cd n (1,4-bdc) n (poly-bpbpvpcb)] ( 2a ). This work not only offers a new protocol to selectively synthesize new supramolecular cyclic compounds, but also expands the application of photopolymerization to the synthesis of macromolecules.