Rational Analysis of Melting Point Behavior of Co-Crystals of 4-Nitrophenol with Some Aza-Compounds

Various co-crystals of 4-nitrophenol with aza-compounds have been synthesized and characterized by single-crystal X-ray diffraction method. Thermal analysis of all the co-crystals infers higher melting point compared to their respective co-formers and the increase in melting point perhaps because of the cross-chain close packed arrangement of the constituent molecules. The trend of increase hi melting point among the co-crystals reported here is difficult to correlate because of the diverse nature of the aza-compounds. Therefore, we have grouped the co-crystals based on the position of the nitrogen atom of aza-compounds: Apart from. structural features the melting point trend among the co-crystals has also been correlated by considering the parameters such as crystal density, packing efficiency, and number of strong hydrogen bonds. It has been noticed that within the group the co-crystal with higher value of above said parameters shows higher melting point compared to the co-crystals with lower values, inferring a linear correlation between any of these parameters and the corresponding melting point of the co-crystal.