Luminescent Cycloplatinated Systems Based on the 2-phenylbenzothiazole Ligand: RelationshipBetween Structure and Optical Properties

Resumen

Over last few decades phosphorescent cyclometalated PtII complexes have receivedexpanding interest due to their potential utility in optical devices, photochemistry, sensorsor biological imaging1. In many occasions the light emitting behaviour of molecular solids,rigid media and concentrated solutions of these complexes differ from their dilute solutionsbecause the occurrence of easy stacking of molecules. In particular, the coordination of flatand delocalized ligands favors Pt···Pt and/or π···π intermolecular interactions, able toproduce extended linear chains and oligomeric nanostructures, which display a richpolymorphism in solid state with alterations in their optical properties.2 These interactionsare sensitive to external stimuli and some of these compounds present mechanochromic orvapochromic behaviour.In this work we describe new PtII compounds based on the 2-phenylbenzothiazole (pbt)fragment as cyclometalated group and bidentate auxiliary ligands L^X, type [Pt(pbt)(L^X)][L^X: PPh2(o-PhCOOH) 2, PPh2(o-PhSO3H) 3, PPh2{(CH2)2COOH} 4, picolinic acid 5 and3-aminopicolinic acid 6], prepared from the DMSO precursor [Pt(pbt)Cl(DMSO)] 1.X-ray diffraction studies show structures self-assembled by hydrogen bonding and/or π···πintermolecular interactions. Interestingly, 6 shows two solid phases, depending on thecrystallization solvent, which display different colors (red and black) and distinct emissionsand 5 is mechanochromic. To insight into the nature of the optical properties, theoreticalanalysis have been carried out at DFT/TD-DFT level for selected complexes and for 5, adimer model (52) has been studied to examine the Non-Covalent Interactions (NCI).