Dihydrogen phosphate-water tape and layers vs dihydrogen phosphate layers tuned by hydrophobic isomeric pyridine-diamine functionalized molecules

Abstract

Assembly of six isomeric pyridine-diamine-based molecules, N,N′-bis(pyridin-4-ylmethyl)ethane-1,2-diamine (M1), N,N′-bis(pyridin-3-ylmethyl)ethane-1,2-diamine (M2), N,N′-bis(pyridin-2-ylmethyl)ethane-1,2-diamine (M3), N,N′-bis(pyridin-4-ylmethyl)propane-1,3-diamine (M4), N,N′-bis(pyridin-3-ylmethyl)propane-1,2-diamine (M5), and N,N′-bis(pyridin-2-ylmethyl)propane-1,3-diamine (M6), with phosphoric acid (H3PO4) in different ratio (1:2 and 1:4), leads to the formation of nine salts, H2M12+·2H2PO4−·4H2O (1), H2M22+·2H2PO4−·2H2O (2), H2M32+·2H2PO4−·2H2O (3), H4M14+·4H2PO4− (4), H4M24+·4H2PO4− (5), H4M34+·4H2PO4− (6), H2M42+·2H2PO4−·3H2O (7), 2H2M52+·4H2PO4−·2H3PO4 (8), and H2M62+·2H2PO4− (9), which have been characterized by elemental analysis, IR, TG, PL, powder and single-crystal X-ray diffraction. Structural analyses indicate that hydrogen-bonding patterns of H2PO4− anions, conformation of protonated cations can effectively influence the supramolecular architectures through diverse non-covalent interactions. Hydrous salts 1–3 and 7 present 2D and 3D host-guest supramolecular networks, in which the connection of H2PO4− anions and water molecules generates diverse tape and layer motifs. H2PO4− anions in anhydrous salts 4–6 interconnect with each other through hydrogen bonds to form two types of layers, which are joined by discrete H4M4+ cations into 3D inorganic-organic hybrid supramolecular networks. Salts 8–9 also present 2D and 3D host-guest supramolecular networks where the interconnection of H2PO4− anions and its combination with H3PO4 molecules leads to diverse layers. Luminescent analyses indicate that salts 1–9 exhibit violet and blue emission maximum in the range of 390–467 nm at room temperature.