Organic Light Emitting Diode (OLED) technology has become considerably commercialized over the last few years due to its superior energy-efficiency. Innovations in this field have been motivated by the discovering of new emissive materials. Desirable OLED candidates present tunable emission wavelengths and large quantum efficiencies. Emissive transition metal complexes take centre stage as potential molecular emitters which facilitate emission from the triplet states (phosphorescence). Tuning of the ground and excited state energies, and thus emission wavelength of these complexes can be achieved by subtle structural changes in the organic ligands. Pyridyl-triazole ligands have started receiving increasing attention in recent years as strong field ligands that are relatively straightforward to synthesise.In this study we explore the emission tunability of a newly synthesised series of 5-subsituted-Pyridyl-1,2,3-triazole-based ligands and their Pt(II) complexes. Studies have shown, substitution at the triazole moiety is less effective in achieving emission tunability. Alternatively we carried out the substitution at the 5th position of the pyridine ring with a wide range of electronically diverse, donor-acceptor groups (-N(CH3)2, -H, -CHO, -CHC(CN)2). As a result, coarse tunability of excimer emission was observed in thin-films, generating blue-(486 nm), green-(541 nm), orange-(601 nm) and red-(625 nm) luminescence respectively. This �turned-on� substituent effect was accounted for metallophilic Pt�Pt interaction-induced aggregates in the solid state. Excited state calculations reveal that the solid state emission is associated with 3??* transitions. Further a linear-relationship between the hammett-parameters of the substituents and emission wavelengths was established. This allows a reliable emission predictability for any given substituent of 5-substituted pyridyl-1,2,3-triazole platinum complexes.In conclusion, we show a new approach in achieving coarse emission tunability in pyridyl-1,2,3-triazole based platinum complexes via subtle changes in the molecular structure and the importance of metallophilic interactions in the process.

Role of metallophilic interactions in �turning on� substituent effects and emission tunability of novel bis-4-(2-pyridyl)-1,2,3-triazolatoplatinum(II) complexes

248th National Meeting (2014)

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