Construction of several new s-/p-block complexes containing binuclear metal–terpyridine building blocks: dependence of structural diversity on the number of coordinated water molecules

Abstract

Five new coordination polymers, [Mg(DSPT)(H₂O)₂]·2H₂O (H₂DSPT = 4′-(2,4-disulfophenyl)-2,2′:6′2′′-terpyridine) (1), {[Ca(DSPT)(H₂O)₂]·1.5H₂O}_n (2), {[Pb(DSPT)(H₂O)]·2H₂O}_n (3), {[Pb(DSPT)]·0.5H₂O}_n (4), and {[Pb₃(DSPT)₃(H₂O)]·8H₂O}_n (5), were prepared under hydrothermal conditions. They are all complexes containing similar M₂L₂ binuclear metal–terpyridine building units. Complex 1 is a discrete binuclear molecule that extends to 2D layers via O–H⋯O hydrogen bonds between coordinated water and a sulfo group on H₂DSPT. Complexes 2 and 3 are 1D coordination chains based on [M₂(DSPT)₂] ring subunits but are connected by different M–O bonds, and the 1D chains are also further connected by O–H⋯O hydrogen bonds between coordinated water and a sulfo group on H₂DSPT to a 2D layer. Complex 4 exhibits a 2D coordination network also based on the [M₂(DSPT)₂] ring subunits. Complex 5 is a by-product of the synthesis of complex 4 that displays a 1D coordination chain structure containing the same [M₂(DSPT)₂] ring subunits. Interestingly, the 2D layers described above show identical skeletons when the bond types between [M₂(DSPT)₂] ring subunits are neglected. The 2D layers in complexes 1–3 can be derived from replacing selected coordination bonds in complex 4 with hydrogen bonds, and such structural diversity is largely dependent on the number of coordinated water molecules around the metal center. Thermogravimetric analyses of 1–4 showed that they were stable at temperatures higher than 500 °C. The luminescent properties of complexes 1–4 were also investigated.