Crystal architectures of copper and zinc metal complexes containing 2-thiophenepropionate and 1,2-bis(4-pyridyl)ethane building blocks

In this work the synthesis, spectroscopic properties (infrared and Raman) and crystal structures of three new coordination polymers named [Cu(2-TPA)(2)](n) (1), {[Zn(bpa)(bpa)(1/2)(2-TPA)].ClO4}(n) (2) and {[Zn-3 (bpa)(4)(2-TPA)(4)].(ClO4)(2)}(n) (3) are reported, where 2-TPA is 2-thiophenepropionate and bpa is 1,2-bis(4-pyridyl) ethane. Compounds 1 and 3 were synthesized by the diffusion method, using methanol/water as solvent for compound 1 and ethanol/water for compound 3. Compound 2 was obtained using solvothermal synthesis, ethanol/water as solvent and with a maximum heating of 90 degrees C. Compounds 1 and 2 crystallize in monoclinic system and space group P2(1)/c: for complex 1 was observed the presence of Cu-Cui bond with distance of 2.587 (2) angstrom, whereas for compound 2 was observed the formation of cavities in the structure. Compound 3 crystallizes in a triclinic system and space group P - 1, with two crystallographically distinct metallic centers named Zn1 and Zn2; the coordination sphere of Zn1 metal ion exhibits slightly distorted octahedral coordination geometry, whereas the other metal site (Zn2) appears in a slightly distorted square-based pyramid ( tau = 0.34). Another important point refers to the synthesis procedure adopted for obtaining different crystalline arrangements involving the same building blocks: by solvothermal or by diffusion, different compounds could be obtained. The vibrational spectra of all the compounds are very similar, and in agreement with the crystal data; the Raman and infrared spectra have shown important bands to confirm the compound formation, such as the coupled v(CC)/v(CN) mode at 1600-1620 cm(-1) (in both Raman and infrared) and v(a)(COO) mode at ca. 1580 cm(-1) (infrared). (C) 2014 Elsevier B.V. All rights reserved.