Solvothermal Syntheses and Physical Properties of Noncentrosymmetric Olefin–Copper(I) Coordination Compounds

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 C3 symmetry of TTB leads to the formation
of a novel C3-symmetric CuX cluster in
oligomer compound 1 (H3TTB­[Cu4Cl3]) and CuX framework
in the two-dimensional compound 2 (H3TTB­[Cu8Br11]). However, the flexibility and kink of H3TTB induce olefin–copper­(I) coordination compounds
to crystallize in noncentrosymmetric space groups R3c and R3 for compounds 1 and 2, respectively. In addition to the bowl-like structure
of the olefin ligand and C3-symmetric
CuX cluster found in compound 1, such bowl-like moieties
are connected by another kind of C3-symmetric
CuX cluster to form a novel two-dimensional framework in compound 2. 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 1 and 2 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 2 correspond
to the higher dielectric constant.