We report the first example of a single molecule (Zn dimer ) containing a s-dimerized 7,7,8,8-tetracyanoquinodimethane (TCNQ). Zn dimer  was synthesized via slow diffusion of Zn(NO3)2, 2,2'-bipyrimidine (bpym) and Li(TCNQ) in methanol, and formed leaf-like purple crystals. The solid state properties were analyzed using single X-ray diffraction, IR spectroscopy, UV-visible-near IR diffuse reflectance spectroscopy, and SQUID. It is composed of two zinc metal centers, each of which is coordinated octahedrally with two bpym and one TCNQ1-. The zinc metal centers are bridged by a dimerized TCNQ ([TCNQ-TCNQ]2-). In each moiety, two bpym ligands are cis disposed to each other, leaving TCNQ1- and [TCNQ-TCNQ]2-cis disposed to each other. In the IR spectrum, ?(C=N) stretch mode is shifted to lower energies, and d(C-H) bend mode validates the presence of [TCNQ-TCNQ]2-. The UV-vis-near IR spectrum shows signals caused by p-stacking of TCNQ, which is supported by the packing diagram. TCNQ1- and [TCNQ-TCNQ]2- are positioned alternatively, forming staircase-shaped stacking pattern. SQUID data suggests that unpaired electrons of TCNQ1- might attribute a very weak paramagnetic property to Zn dimer  . In addition, the solution phase behavior was investigated using cyclic voltammetry, UV-vis spectroscopy and IR spectroscopy. The first two techniques demonstrate identical properties to a single molecule, TCNQ1-. The IR spectrum of the chemically reduced species displays disproportionation of Zn dimer . Figure 1. Crystal structure of Zn dimer  . All hydrogen atoms are removed for simplicity.

Magnetic, spectroscopic, and structural properties of a trans-�2-[TCNQ-TCNQ]2- bridged zinc complex

247th National Meeting (2014)

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