A DFT investigation on the effect of ligand substitution on photophysicalproperties of some new cyclometalated Ir(III) complexes

Cyclometalated Ir(III) complexes has attracted considerable attention due to theirapplications in electroluminescence, photocatalysis, phosphorescent molecular probes [۱] andtheir potential for solid-state lighting and display utilizations [۲]. The complexes are morepromising because of larger d-orbital splitting and strong spin-orbit coupling (SOC) effect [۳].Phosphorescent cyclometalated Ir(III) complexes usually represent high quantum yields andemissive metal to ligand charge transfer (۳MLCT) excited states. Ir(III) ion, due to the high SOC,facilitates the intersystem crossing of the excited states. Moreover, the forbidden T۱ →S۰ transition is activated in these complexes [۴]. Here, electronic structure of four newcyclometalated Ir(III) complexes are studied at DFT/B۳LYP level of theory. Previously, themethod has been successfully applied to investigate Ir(III) complexes [۵]. The effect offunctionalization of ancillary ligand by benzothiazole derivatives (as electron acceptor) andelectron donor groups on the electronic structure of the complexes are investigated. It is wellknown that, the electrochemical and photophysical properties of these complexes could be tunedby functionalization of the ancillary ligand [۴]. Photophysical properties of the compounds arestudied by TDDFT method at the same level of theory.