Facile synthesis of 6-aryl-3-pyridyl-1,2,4-triazines as a key step toward highly fluorescent 5-substituted bipyridines and their Zn(II) and Ru(II) complexes

A wide series of substituted bipyridines were obtained through the synthesis of 1,2,4-triazines and their aza Diels–Alder reactions. The reported method facilitates the synthesis of functionally diverse bipyridines that provides fine-tuning of photophysical properties of new ligands and their Zn(II) and Ru(II) complexes. Some of substituted bipyridines exhibit ‘off–on’ fluorescence response toward Zn2+ cations.