Spectroscopic, thermal, and magnetic properties of metal/TCNQ network polymers with extensive supramolecular interactions between layers

Reactions of [M(MeCN)(n)][BF4](2) salts with Bu4N(TCNQ) in MeOH yield M(TCNQ)(2)(MeOH)(x) (M = Mn, 1; Fe, 2; Co, 3; Ni, 4, x = 2-4), and reactions of MnCl2, FeSO4. 7H(2)O, CoSO4. 7H(2)O and NiCl2. 6H(2)O in H2O produce M(TCNQ)(2)(H2O)(2) (M = Mn, 5; Fe, 6; Co, 7; Ni, 8). Infrared spectroscopy, powder X-ray diffraction and thermogravimetric analyses of 1-8 indicate that the products prepared in the same solvent constitute isostructural families of compounds. [Mn(TCNQ-TCNQ)(MeOH)(4)](infinity) (9) crystallizes in the triclinic space group P (1) over bar, a = 7.2966(8) A, b = 7.4289(8) Angstrom, c = 14.060(2) Angstrom, alpha = 76.112(2)degrees beta = 87.242(2)degrees, gamma = 71.891(2)degrees, V = 702.91(13) Angstrom(3), Z = 1; [Mn(TCNQ)(TCNQ-TCNQ)(0.5)(MeOH)(2)](infinity) (10) crystallizes in the monoclinic space group C2/c, a = 14.4378(5) Angstrom, b = 27.3067(11) Angstrom, c = 13.1238(5) Angstrom, beta = 90.057(1)degrees V = 5174.0(3) Angstrom(3), Z = 8. Compound 9 contains TCNQ(-) ligands that have undergone an unusual sigma-dimerization to [TCNQ-TCNQ](2-) that acts as a tetradentate ligand to Mn(II) ions to give a 2-D staircase polymeric motif. The layers are connected by hydrogen-bonds between axially coordinated MeOH from adjacent layers and MeOH located between the layers. Compound 10 exhibits a zigzag polymeric motif with equatorially bound TCNQ-derived ligands of two types; the edges of the layers consist of cis-mu-TCNQ(-) molecules involved in sr-stacking with TCNQ(-) units from another layer and sigma-[TCNQ-TCNQ]2- acting as a tetradentate bridging ligand. Axial MeOH ligands are hydrogen-bonded to dangling nitrile groups of cis-mu-TCNQ(-) ligands in the next layer. Mn(TCNQ)(2)(H2O)(2) (11) crystallizes in the monoclinic space group I2/a a = 12.5843(7) Angstrom, b = 13.7147(7) Angstrom, c = 13.3525(70 Angstrom, beta = 92.887(1)degrees V = 2301.58 Angstrom(3), Z = 4. This material adopts a double-layer motif consisting of Mn(II) ions bonded to syn-mu(2)-TCNQ(-) equatorial ligands and axial H2O molecules. Compounds 1-11 exhibit Curie-Weiss behavior with weak antiferromagnetic coupling being observed at low temperatures. The Zn(II) analogue of 10, [Zn(TCNQ!(TCNQ-TCNQ)(0.5)(MeOH)(2)](infinity) (12) was also prepared: space group C2/c, a = 14.2252(1) Angstrom, b = 27.3290(4) Angstrom, c = 13.1177(2) Angstrom, beta = 90.074(1)degrees, V = 5099.64(11) Angstrom(3), Z = 8. Powder X-ray diffraction was used to probe structures 1-11, and it was found that 9 converts to a new phase with heating or exposure to X-rays that is related to disruption of the sigma-dimer (TCNQ-TCNQ)(2-) ligands and loss of MeOH. The new phase, whose powder pattern is identical with that of a phase prepared from MeCN, exhibits ferromagnetic behavior.