Mixed-ligand Mn-II and Cu-II complexes with alternating 2,2 '-bipyrimidine and terephthalate bridges

Abstract

The novel polymeric complexes catena-poly[[diaquamanganese(II)]-mu-2,2'-bipyrimidine-kappa N-4(1),N-1':N-3,N-3'-[diaquamanganese(II)]-bis(mu-terephthalato-kappa O-2(1):O-4)], [Mn-2(C8H4O4)(2)(C8H6N4)(H2O)(4)](n), (I), and catena-poly[[[aquacopper(II)]-mu-aqua-mu-hydroxido-mu-terephthalato-kappa O-2(1):O-1'-copper(II)-mu-aqua-mu-hydroxido-mu-terephthalato-kappa O-2(1):O-1'-[aquacopper(II)]-mu-2,2'-bipyrimidine-kappa N-4(1),N-1':N-3,N-3'] tetrahydrate], {[Cu-3(C8H4O4)(2)- (OH)(2)(C8H6N4)(H2O)(4)]center dot 4H(2)O}(n), (II), containing bridging 2,2'-bipyrimidine (bpym) ligands coordinated as bis-chelates, have been prepared via a ligand-exchange reaction. In both cases, quite unusual coordination modes of the terephthalate (tpht(2-)) anions were found. In (I), two tpht(2-) anions acting as bis-monodentate ligands bridge the Mn-II centres in a parallel fashion. In (II), the tpht(2-) anions act as endo-bridges and connect two Cu-II centres in combination with additional aqua and hydroxide bridges. In this way, the binuclear [Mn-2(tpht)(2)(bpym)(H2O)(4)] entity in (I) and the trinuclear [Cu-3(tpht)(2)(OH)(2)(bpym)(H2O)(4)]center dot 4H(2)O coordination entity in (II) build up one-dimensional polymeric chains along the b axis. In (I), the Mn-II cation lies on a twofold axis, whereas the four central C atoms of the bpym ligand are located on a mirror plane. In (II), the central Cu-II cation is also on a special position (site symmetry 1). In the crystal structures, the packing of the chains is further strengthened by a system of hydrogen bonds [in both (I) and (II)] and weak face-to-face pi-pi interactions [in (I)], forming three-dimensional metal-organic frameworks. The Mn-II cation in (I) has a trigonally deformed octahedral geometry, whereas the Cu-II cations in (II) are in distorted octahedral environments. The Cu-II polyhedra are inclined relative to each other and share common edges.