Luminescence\nBehavior of Cationic and Neutral Cu<sup>I</sup> Complexes of Phosphine\nand Pyridine Embedded 1,2,3-Triazole

Synthesis of a potentially polydentate, phosphine and\npyridine\nembedded 1,2,3-triazole, <i>o</i>-Ph<sub>2</sub>P(C<sub>6</sub>H<sub>4</sub>)C(CH)-1,2,3-N<sub>3</sub>(CH<sub>2</sub>)(Py)\n(<b>1</b>) (here onward referred to as “P<sup>∩</sup>N<sub>3</sub><sup>∩</sup>N”) and its copper complexes\nare described. Reactions of <b>1</b> with CuX yielded mononuclear\n[Cu{(P<sup>∩</sup>N<sub>3</sub><sup>∩</sup>N)<sub>2</sub>-κ<sup>2</sup>-<i>P,N</i>}]X (<b>2</b> – <b>4</b>; X = I, CuBr<sub>2</sub> and CuCl<sub>2</sub>) and dinuclear\n[Cu<sub>2</sub>{(P<sup>∩</sup>N<sub>3</sub><sup>∩</sup>N)<sub>2</sub>-κ<sup>4</sup>-<i>P,N,N,N</i>}]X (<b>5</b> X = OTf, <b>6</b> X = BF<sub>4</sub>) complexes. Interestingly,\nthe cationic complex [Cu{(P<sup>∩</sup>N<sub>3</sub><sup>∩</sup>N)<sub>2</sub>-κ<sup>2</sup>-<i>P,N</i>}]I (<b>2</b>) in acetonitrile changes into neutral complex [Cu<sub>3</sub>(μ<sub>2</sub>-I)<sub>2</sub>(μ<sub>3</sub>-I)(NCCH<sub>3</sub>){(P<sup>∩</sup>N<sub>3</sub><sup>∩</sup>N)-κ<sup>4</sup>(μ<sub>2</sub>-<i>P,N</i>)(μ<sub>2</sub>-<i>N,N</i>)}](<b>7</b>), which on addition of dichloromethane\nreverts back to the cationic form. The photoluminescent characteristics\nof cationic complexes are significantly impacted by the nature of\ncounteranions and hence the corresponding photoluminescence quantum\nyields. Cationic complex <b>2</b> showed an increase in quantum\nyield and lifetime on changing over to neutral complex <b>7</b>. TD-DFT calculations also assisted in assessing the photophysical\nproperties.