Weak C–H…O Interactions Leading to Measurable Effects in Polymeric Sulfates [M(SO4)L(H2O)2]n (M = Cd, Zn, Cu; L = bipy, phen, dmp)

Abstract

The structure of two sulfate complexes, [Zn(SO₄)phen(H₂O)₂]_n and [Cd(SO₄)bipy(H₂O)₂]_n, are presented. They are polymeric and isomorphous to an homologous series already reported, namely [Zn(SO₄)bipy(H₂O)₂]_n, [Cd(SO₄)dmph(H₂O)₂]_n, [Cu(SO₄)bipy(H₂O)₂]_n, and [Cu(SO₄)phen(H₂O)₂]_n (bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline). The compounds organize into double polymeric chains internally linked through strong (O–H)_water^…O_sulfate bonds. The interaction between these ‘strips’ is governed by weak (C–H)_ligand^…O_sulfate bonds, which explain a seemingly abnormal expansion/contraction of some cell parameters in the homologous series. Both compounds are monoclinic, C2/c. [Zn(SO₄)phen(H₂O)₂]_n: a 15.156(3), b 14.152(3), c 6.7010(13) Å, β 103.43(3)°, V 1398.0(5) ų, Z 4, conventional R (on F) being 0.028 for N_o 1615 observed reflections (I >2σ(I)). [Cd(SO₄)bipy(H₂O)₂]_n: a 15.705(3), b 13.049(3), c 6.8912(14) Å, β 104.59(3)°, V 1366.7(5) ų, Z 4, R 0.052, N_o 1516.