Influence of solvents and assembly methods on the supramolecular patterns and luminescent properties of organic salts comprising 4,4′-dihydroxybiphenyl-3,3′-disulfonate and triphenylmethanaminium

Abstract

DO = 1,4-dioxane) have been obtained from the reaction of H 4 M and TPMA in different solvents by two assemble methods and characterized by elemental analysis, IR, TG, PL, powder and single-crystal X-ray diffraction. Structural analyses indicate that the nature of the solvent molecules can effectively influence the ···(-SO 3 )··· (-15 NH 3 )···(solvent)··· patterns, which then result in diverse packing diagrams. In salts 1 and 3, pairs of HTPMA + cations arrange in tail-to-tail mode to form column motifs which are extended the layers of H 2 M 2dianions into pillared layered network. On the contrary, pairs of HTPMA + cations in salt 2 arrange in head-to-head mode and form layer structures together with pairs of H 2 M 2dianions. The HTPMA + cations and H 2 M 2dianions in salts 4 and 6 are alternately arranged to form column motif, which then 20 pack with each other to form supramolecular network. Pairs of head-to-head HTPMA + cations in salts 7-9 are sandwiched between the -SO 3 groups through hydrogen bonding interactions, generating graphite-like structure. The HTPMA + cations in salts 5 and 10-12 arrange in tail-to-tail mode to form column motifs which are then sandwiched between biphenyl rings instead of the -SO 3 groups. Moreover, different assemble processes are also responsible for diverse structures. Small solvent molecules, such as H 2 O and 25 MeOH, tend to form different structures (1 and 2, 3 and 4), while large molecules usually present the same structures (6-12). It is interesting to note that salt 4 can transform into salt 5 after being exposed to the air for several hours. Luminescent investigation reveals that the emission maximum of salts 1-12 varies from 365 to 371 nm.

Structural variation from linear, layer to 3D framework: Syntheses, structures and luminescence

“…For complexes 1–3 , the emission intensity show solvent‐dependent change. Usually, high polar solvents cause decreasing of emission intensity . In this sense, complexes 1 and 2 exhibit lower emission intensity than that of solvent‐free complex 3 owing to the lattice and coordinate water molecules involved in their molecular structure.…”

“…Such conjugated system offers more electrons to improve the energy level of HOMO in aromatic rings and subsequently decrease the energy gap between HOMO and LUMO, thus increasing the chance of intraligand charging transfer . In addition, the stronger emission intensity of complex 4 rather than that of complex 5 is ascribed to the formation of strong π···π stacking interactions, which could increase the chance of intraligand charge transfer and further enhance the emission intensity . For complexes 1–3 , the emission intensity show solvent‐dependent change.…”