Tetrathiafulvalene-Triazine-Dipyridylamines as Multifunctional Ligands for Electroactive Complexes: Synthesis, Structures, and Theoretical Study

The electroactive ligands (2,4-bis-tetrathiafulvalene[6-(dipyridin-2′-ylamino)]-1,3,5-triazine) TTF2-tz-dpa (1) and (2-tetrathiafulvalene[4,6-bis-(dipyridin-2′-ylamino)]-1,3,5-triazine) TTF-tz-dpa2 (2) have been synthesized by palladium cross-coupling catalysis, and the single crystal X-ray structure for 1 was determined. In the solid state the TTF and triazine units are practically coplanar and short intermolecular S···S contacts are established. Two neutral and one tetracationic Zn(II) complexes, formulated as (TTF2-tz-dpa)ZnCl2 (3), [ZnCl2(TTF-tz-dpa2)Zn(H2O)Cl2] (4), and {[(H2O)2Zn(TTF-tz-dpa2)](ClO4)2}2 (5) have been crystallized and analyzed by single crystal X-ray analysis. A peculiar feature is the evidence for anion-π interactions, as shown by the short Cl···triazine and O(perchlorate)···triazine distances of 3.52 and 3.00 Å, respectively. A complex set of intermolecular π···π, S···S, and hydrogen bonding interactions sustain the supramolecular organizations of the complexes in the solid state. Electronic absorption spectra provide evidence for the intramolecular charge transfer from TTF to triazine, also supported by time-dependent density functional theory (TD DFT) calculations.