Synthesis, Structures and Photoluminescence Properties of a Series of Alkaline Earth Metal-Based Coordination Networks Synthesized Using Thiophene-Based Linkers

Three new 3-D coordination networks were synthesized
using alkaline-earth
metal centers, calcium, and strontium, with 2,5-thiophenedicarboxylate
(TDC) as the organic linker. [Ca2(TDC-2H)2(DMF)2]n [1, space group P21/n, a =
10.0704(3) Å, b = 14.2521(3) Å, c = 17.5644(6) Å, β = 94.281(2)°] is composed
of tetrameric calcium polyhedral clusters, which are connected by
the organic linkers. Coordinated DMF molecules are present within
the 1-D channel along the [010] direction. [Ca­(TDC-2H)]n [2, space group Pbcm, a = 5.3331(5) Å, b = 6.8981(4)
Å, c = 18.141(2) Å] consists of chains
of edge-sharing calcium octahedra, connected by organic linkers, to
form a dense network. [Sr­(TDC-2H)­(DMF)]n [3, space group P21/n, a = 5.9795(3) Å, b = 17.058(1) Å, c = 11.3592(6) Å, β
= 91.257(1)°] forms a structural topology almost identical to
compound 1 except that the chains are built by combinations
of edge- and face-sharing polyhedra. Compounds 1 and 3 were synthesized using DMF as solvent, whereas compound 2 crystallizes using ethanol. Photoluminescence studies reveal
that the topologies of the networks and the presence of the coordinated
solvent molecules control the luminescence properties of the compounds.