Mixed-ligand Mn^IIand Cu^IIcomplexes with alternating 2,2′-bipyrimidine and terephthalate bridges

Abstract

The novel polymeric complexes catena-poly[[diaquamanganese(II)]-μ-2,2'-bipyrimidine-κ(4)N(1),N(1'):N(3),N(3')-[diaquamanganese(II)]-bis(μ-terephthalato-κ(2)O(1):O(4))], [Mn2(C8H4O4)2(C8H6N4)(H2O)4]n, (I), and catena-poly[[[aquacopper(II)]-μ-aqua-μ-hydroxido-μ-terephthalato-κ(2)O(1):O(1')-copper(II)-μ-aqua-μ-hydroxido-μ-terephthalato-κ(2)O(1):O(1')-[aquacopper(II)]-μ-2,2'-bipyrimidine-κ(4)N(1),N(1'):N(3),N(3')] tetrahydrate], {[Cu3(C8H4O4)2(OH)2(C8H6N4)(H2O)4]·4H2O}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 [Mn2(tpht)2(bpym)(H2O)4] entity in (I) and the trinuclear [Cu3(tpht)2(OH)2(bpym)(H2O)4]·4H2O 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 π-π 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.