Solvothermal Syntheses
and Physical Properties of
Noncentrosymmetric Olefin–Copper(I) Coordination Compounds
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Abstract
Solvothermal reactions of CuX (X = Cl, Br) and the organic
olefin
ligand 1,3,5-tris(diallylaminomethyl)-2,4,6-trimethylbenzene (TTB)
in the presence of acid offered two novel olefin–copper(I)
coordination compounds with unprecedented CuX cluster structures.
The <i>C</i><sub>3</sub> symmetry of TTB leads to the formation
of a novel <i>C</i><sub>3</sub>-symmetric CuX cluster in
oligomer compound <b>1</b> (H<sub>3</sub>TTB[Cu<sub>4</sub>Cl<sub>3</sub>]) and CuX framework
in the two-dimensional compound <b>2</b> (H<sub>3</sub>TTB[Cu<sub>8</sub>Br<sub>11</sub>]). However, the flexibility and kink of H<sub>3</sub>TTB induce olefin–copper(I) coordination compounds
to crystallize in noncentrosymmetric space groups <i>R</i>3<i>c</i> and <i>R</i>3 for compounds <b>1</b> and <b>2</b>, respectively. In addition to the bowl-like structure
of the olefin ligand and <i>C</i><sub>3</sub>-symmetric
CuX cluster found in compound <b>1</b>, such bowl-like moieties
are connected by another kind of <i>C</i><sub>3</sub>-symmetric
CuX cluster to form a novel two-dimensional framework in compound <b>2</b>. The electron cloud distributions and energy levels of the
frontier orbitals in both compounds have been calculated by a DFT
program. Nonlinear optical property measurement results show that
both compounds are second-harmonic generation (SHG) active. Compounds <b>1</b> and <b>2</b> display no phase transition according
to the measurement of the temperature dependence of dielectric properties
in the temperature range 100–300 K. The close packing and large
density from the high CuX/ligand ratio in compound <b>2</b> correspond
to the higher dielectric constant