Role of incorporated SCN− or SO42− in organically templated chlorocadmates: synthesis, structural characterization and photoluminescence property

Abstract

Based on an aim of introducing the SCN− or SO42− group into the organically templated chlorocadmates, a series of room-temperature reactions at pH 2 were performed, creating four new Cd(II) hybrids as [L1]4[Cd4Cl6(SCN)10(H2O)2] (L1=1,1′-dibenzyl-4,4′-bipyridium) 1, [H4L2][CdCl4(SCN)2] (L2=1,4-bis(4-pyridylmethyl)piperazine) 2, [HL3]3[CdCl3]SO4 (L3=2-amino-6-chloropyridine) 3, and [HL4]3[CdCl3]SO4 (L4=2-amino-6-bromopyridine) 4. X-ray single-crystal diffraction analysis reveals that (i) templated by L12+, 1 shows a 1-D single-chain structure, which is based on the dinuclear [Cd2Cl3(SCN)4(H2O)]3− clusters by the μ-1,3-mode SCN− groups; (ii) templated by H4L24+, 2 only exhibits a mononuclear structure. However, via the intermolecular weak NpyridineH⋯Cl, NpiperazineH⋯Cl and SSCN⋯SSCN interactions, 2 self-assembles into a 3-D supramolecular network with a (4,6)-connected topology; (iii) 3 and 4 possess the similar structures. Via the Npyridine/aminoH⋯O and π⋯π interactions, the introduced SO42− groups and the organic base molecules aggregate together into a 3-D supramolecular network with the 1-D channels. Within the channel, the Cl− ions triplely bridge the Cd2+ centers into a 1-D linear [CdCl3]− chain. Based on the structural information and the previous related reports, the role of the introduced SCN− or SO42− group in the hybrid is revealed. SCN− acts as two roles: (i) a linker; (ii) a cutter. Sometimes SO42− serves as a linker, while sometimes SO42− connects with organic base into a supramolecular aggregation, acting as a new templating agent. The photoluminescence analysis reveals that 2, 3 and 4 emit light with the maxima at 535nm for 2 (λex=465nm), 462nm for 3 (λex=428nm), and 465nm for 4 (λex=430nm), respectively. In particular, the emissions for all are strong, and can be seen under the ultraviolet (UV) lamp.