One-Dimensional Coordination Polymers of Bis(3-pyridyl-acrylamido)ethane: Influence of Anions and Metal Ions on Their Solid State [2 + 2] Photochemical Polymerization and Dimerization Reactions

The coordination polymers (CPs) of bis­(3-pyridyl-acrylamido)­ethane (L) with nitrate, acetate, and perchlorate salts of Cu­(II), Cd­(II), and Zn­(II) were synthesized, and their crystal structures have been analyzed with respect to the influence of anions, hydrogen bonding, and their solid state [2 + 2] photochemical reactivity. Four out of the six CPs (1–4) containing NO₃^– and AcO^– ions were found to form one-dimensional chains and exhibit solid state [2 + 2] reactivity. Two CPs (5–6) containing ClO₄^– ions were found to form ML₂ discrete complexes which are photostable. The CPs 1 and 4 were found to form single [2 + 2] dimers, while 2 and 3 resulted in the formation of polymers via solid state [2 + 2] polymerization upon irradiation. The photoproducts are characterized by ¹H NMR, electrospray ionization mass spectrometry, and matrix-assisted laser desorption/ionization–time of flight (MALDI-TOF) spectra. The dimer was charecterized by single crystal X-ray structure determination. The MALDI-TOF analyses of polymers indicate the highest degree (29-mer) of polymerization.