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

Twelve organic salts, namely 2(HTPMA)⁺·(H₂M)²⁻·4(H₂O) (1), 2(HTPMA)⁺·(H₂M)²⁻·2(H₂O) (2), 2(HTPMA)⁺·(H₂M)²⁻·2(MeOH)·(H₂O) (3), 2(HTPMA)⁺·(H₂M)²⁻·4(MeOH) (4), 2(HTPMA)⁺·(H₂M)²⁻·(MeOH) (5), 2(HTPMA)⁺·(H₂M)²⁻·2(EtOH)·2(H₂O) (6), 2(HTPMA)⁺·(H₂M)²⁻·2(n-PrOH) (7), 2(HTPMA)⁺·(H₂M)²⁻·2(n-BuOH) (8), 2(HTPMA)⁺·(H₂M)²⁻·2(n-PeOH) (9), 2(HTPMA)⁺·(H₂M)²⁻·2(DO) (10), 2(HTPMA)⁺·(H₂M)²⁻·2(DMF) (11), and 2(HTPMA)⁺·(H₂M)²⁻·2(DMSO) (12) (H₄M = 4,4′-dihydroxybiphenyl-3,3′-disulfonic acid, TPMA = triphenylmethylamine, DO = 1,4-dioxane) have been obtained from the reaction of H₄M and TPMA in different solvents by two assembly 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 ⋯(–SO₃)⋯(–NH₃)⋯(solvent)⋯ patterns, which then result in diverse packing diagrams. In salts 1 and 3, pairs of HTPMA⁺ cations arrange in a tail-to-tail mode to form column motifs which extend the layers of H₂M²⁻ dianions into a 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 H₂M²⁻ dianions. The HTPMA⁺ cations and H₂M²⁻ dianions in salts 4 and 6 are alternately arranged to form a column motif, which then pack with each other to form a supramolecular network. Pairs of head-to-head HTPMA⁺ cations in salts 7–9 are sandwiched between the –SO₃ groups through hydrogen bonding interactions, generating a 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 –SO₃ groups. Moreover, different assembly processes are also responsible for the diverse structures. Small solvent molecules, such as H₂O and 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. Luminescence investigation reveals that the emission maximum of salts 1–12 varies from 365 to 371 nm.