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From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
Photoluminescent chain-of-dimer anion in a novel hybrid halometallate (C5H14N2)3{Sb2Br9}2: atypical behavior in
Andrei V Bykov1, Tatiana A Shestimerova1, Mikhail A Bykov1
1Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia. shev@inorg.chem.msu.ru.
Abstract:
In pursuit of identifying less toxic hybrid compounds suitable for optoelectronic applications, we synthesized a novel homopiperazinium bromoantimonate(III), (C5H14N2)3{Sb2Br9}2. It readily crystallized from an aqueous hydrobromic acid solution and was found to be stable both in air and upon heating up to 175 °C. The crystal structure of the new bromoantimonate(III) consisted of {Sb2Br9}3- zigzag chains, which were composed of strongly trigonally distorted SbBr63- octahedral anions and C5H14N22+ dications. Weak interactions, including (N)H⋯Br hydrogen bonds and Br⋯Br van der Waals contacts, facilitated the assembly of the structural moieties into a three-dimensional (3D) supramolecular framework. The photoluminescence (PL) spectrum of (C5H14N2)3{Sb2Br9}2 displayed two broad bands in visible and near-infrared regions, which were scarcely detectable at room temperature but gained intensity upon cooling. Red emission at 645 nm, typically observed in zero-dimensional halometallates, was attributed to antimony 5s2 lone-pair-driven luminescence that corresponded to the emission from the self-trapped exciton (STE) state. The title compound also exhibited an atypical PL band at 880 nm, which has been discussed along with the optical properties and Raman spectrum of (C5H14N2)3{Sb2Br9}2.
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