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Polyoxomolybdates co-ordinated by glycyl-glycine: Structures of Na_4[Mo_8O_2_6(glygly)_2] . 15H_2O (I) and Na_4[Mo_8O_2_6(glygly)_2] . 12H_2O (II)

It has been observed that polyoxomolybdates exhibit antitumor activity.1 Therefore, structural chemistry of polyoxomolybdates with organic ligands is essential for understanding their antitumor or antiviral activities. Here we describe the crystal structures of two gama-type octamolybdates coordinated with glycyl-glicine. Crystal data: (I) Na_4[Mo_8O_2_6(glygly)_2] . 15H2O, Mr = 1801.9, triclinic, a = 10.945(5), b = 11.530(4), c = 11.870(5) Å, alfa = 64.70(3)A beta = 64.26(3)A gama = 82.83(3)A, V = 1231.6(9) Å^3, Z = 2, space group , Dcalc = 2.465 g cm^-^3, F(000) = 870, *(MoK*) = 0.7107 Å . (II) Na_4[Mo_8O_2_6(glygly)_2] . 12H_2O, Mr = 1753.9 , triclinic , a = 9.4207(8), b = 11.3205(8), c = 11.8201(11) Å, alfa = 63.896(6)A beta = 74.109(7)A gama = 82.371(7)A, V = 1088.63(16) Å^3, Z = 2, space group , Dcalc = 2.675 g cm^-^3, F(000) = 846, *(MoK*) = 0.7107 Å . Both crystal structures consist of centrosymmetric -octamolybdate [Mo_8O_2_6]^4^- anions, sodium cations and water molecules. The anions in (I) and (II) are built up of eight edge sharing MoO6 octahedra with the usual distribution of metal-to-oxygen bond lenghts: two short Mo-O bonds [from 1.704(2) to 1.751(2) Å], two bonds of intermediate lenght [from 1.876(2) to 1.967(2) Å] and two long bonds [from 2.135(2) to 2.453(2) Å]. Dipeptide glycyl-glycine is coordinated via monodentate carboxylate-oxygen atom occupying the vacant sites of two five coordinated molybdenum atoms in the centrosymmetric beta-[Mo_8O_2_6]^4^- anions. It has been observed that glycyl-glycine molecules have different conformations. The water molecules are hydrogen bonded to the terminal and bridging oxygen atoms. Sodium cations are octahedrally coordinated by oxygen atoms from the anion and water molecules thus forming edge sharing octahedra.

glycyl-glycine; polyoxomolybdates; antiviral activities

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