Synthesis and Structural Characterization of Five New Coordination Polymer Chain Structures Using A New, Z-Shaped Ligand, 2,2′-bis-(4-Pyridylethynyl)Tolane

Jeffrey E. Fiscus, University of South Carolina - Columbia
Neil Pschirer, University of South Carolina - Columbia
Rachael E. Hipp, University of South Carolina - Columbia
Andrea M. Goforth, University of South Carolina - Columbia
Craig Chapman, University of South Carolina - Columbia
Sandra Shotwell, University of South Carolina - Columbia
Ralph C. Layland, Lander University
Mark D. Smith, University of South Carolina - Columbia
Uwe H. F. Bunz, University of South Carolina - Columbia
Hans-Conrad zur Loye, University of South Carolina - Columbia

Abstract

Using the new ligand, 2,2′-bis-(4-pyridylethynyl)tolane we have synthesized five new coordination polymers: HgBr₂[2,2′-bis-(4-pyridylethynyl)tolane] (1), HgI₂[2,2′-bis-(4-pyridylethynyl)tolane] (2), Ni(acetylacetonate)₂[2,2′-bis-(4-pyridylethynyl)tolane] (3), Zn(acetylacetonate)₂[2,2′-bis-(4-pyridylethynyl)tolane] (4), and Cu(hexafluoro acetylacetonate)₂[2,2′-bis-(4-pyridylethynyl)tolane]⋅CHCl₃(5). 2,2′-Bis-(4-pyridyl ethynyl)tolane is a rigid ligand with a Z-shape that promotes the formation of zig-zag chains. Compounds 1– 5 were characterized by single crystal X-ray diffraction; and compounds 1– 3 were additionally characterized by IR, elemental analysis, and thermogravimetric analysis. Compound 1 crystallizes in the monoclinic space group C₂/c with a = 29.761(3) Å, b = 5.0531(5) Å, c = 16.7823(15) Å, β = 104.090(2)∘, V = 2447.9(4) Å3, Z = 4. Each mercury is bound to two tolane ligands and two bromine anions, resulting in a tetrahedral coordination environment. Compound 2 crystallizes in the monoclinic space group P₂/c, with a = 20.3061(17) Å, b = 5.6303(5) Å, c = 24.5459(19) Å, β = 110.338(2)∘, V = 2631.4(4) Å3, Z = 4. Here also, each mercury is bound to two tolane ligands and two iodine anions in a tetrahedral coordination environment. The ligand orientation differs in compounds 1 and 2 being trans oriented in 1 and cis oriented in 2. Compound 3 crystallizes in the monoclinic space group P₂₁/c with a = 14.5947(14) Å, b = 6.3082(6) Å, c = 18.3939(18) Å, β = 112.112(2)∘, V = 1568.9(3) Å3, Z = 2. Each nickel is bound to two tolane ligands and two bidentate AcAc anions, resulting in an octahedral coordination environment. Compound 4, which is isostructural with 3, also crystallizes in the monoclinic space group P₂₁/c with a = 14.6990(9) Å, b = 6.2724(4) Å, c = 18.6433(11) Å, β = 112.8610(10)∘, V = 1583.86(17) Å3, Z = 2. Compound 5 crystallizes in the triclinic space group P-1 with a = 6.5487(4) Å, b = 11.6471(7) Å, c = 14.3225(9) Å, α = 70.1360(10)∘, β = 89.3990(10)∘, γ = 88.7680(10)∘, V = 1027.18(11) Å3, Z = 1. Each copper in 5 is bound to two tolane ligands and two bidentate hfAcAc anions, resulting in an octahedral coordination environment identical to that found in 3 and 4.