Synthesis of novel triarylamine-based dendrimers with N-4,N-6-dibutyl-1,3,5-triazine-4,6-diamine probe for electron/energy transfers in H-bonded donor-acceptor-donor triads and as efficient Cu2+ sensors

Abstract

Two novel highly soluble triarylamine dendrimers TPAD1 and TPAD2 with N-4,N-6-dibutyl-1,3,5-triazine-4,6-diamine probe were synthesized via normal synthetic routes. Both dendrimers (TPAD1 and TPAD2) form H-bonded donor-acceptor-donor (D-A-D) supramolecular triads TPAD1-PBI-TPAD1 and TPAD2-PBI-TPAD2 with 3,4,9,10-perylene tetra carboxylic diimide derivative (PBI). The presence of multiple H-bonds in the solution state was elucidated by H-1 NMR titrations and IR spectral studies. J-aggregations and electron/energy transfers provided by both dendrimers were verified by UV-Vis and photoluminescence (PL) titrations with PBI and the particle sizes of supramolecular triads were calculated by X-ray diffraction (XRD) analysis. Similarly, both dendrimers also showed sensitivities towards Cu2+ in comparison with 19 interfering metal ions, which were evidenced via UV-Vis and PL titraions in both single and dual metal systems. The maximum detection limit of Cu2+ ions was determined to be 20 ppm from PL titrations for both dendrimers, and the 1 : 2 stoichiometry of the complexes formed by both dendrimers (TPAD1-Cu2+ and TPAD2-Cu2+) were calculated by Job plots based on UV-Vis absorption titrations. More importantly, the binding mechanism of the 1,3,5-triazine-4,6-diamine probe of both dendrimers was well characterized by H-1 and C-13 NMR titrations ([D-8] THF : D2O = 2 : 1 in vol.) and supported by the fluorescence reversibility by adding metal ions and PMDTA sequentially.