Formation of Zn(II) and Cd(II) coordination polymers assembled by triazine-based polycarboxylate and in-situ-generated pyridine-4-thiolate or dipyridylsulfide ligands: observation of an unusual luminescence thermochromism

Three novel coordination polymers, Cd(5)(HTTHA)(2)(Hpt)(4)(H(2)O)]·4H(2)O (1; H(6)TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid, Hpt = pyridinium-4-thiolate), {Cd(3)(TTHA)(dps)(H(2)O)(3)](2)}·H(2)O (2), and Zn(3)(TTHA)(dps)(H(2)O)]·5H(2)O (3; dps =4,4'-dipyridylsulfide), have been synthesized by the flexible hexapodal acid H(6)TTHA and in-situ-generated Hpt and dps ligands from a 4,4'-dipyridyldisulfide (dpds) precursor through cleavage of both S-S and S-C(sp(2)) bonds and temperature-dependent chemical rearrangement under hydrothermal conditions. Polymers 2 and 3 exhibit 3D frameworks, while in 1, the extended 3D network can be described as 2D layers further bridged via H-bond interaction. Intriguingly, the three compounds have shown an unusual luminescence thermochromism. Upon decreasing the temperature from 298 to 10 K, the emission bands grow in intensity and change in color dramatically.