Synthesis, Spectral Characterization, Thermal and Optical Studies of Novel Complexes: 4-(Dimethylamino)benzylidene-4-acetamideaniline and 4-(Dimethylamino)benzylidene-4-nitroaniline

The phase diagram representing solid–liquid equilibrium of entire range of composition and thermodynamic studies of two binary organic systems of 4-dimethylaminobenzaldehyde (DMAB) with two NLO active compounds, p-aminoacetanilide (PAA) and p-nitroaniline (PNA), have been studied by solid state synthetic route. Both systems are independently forming a new entity called intermolecular complex (IMC) and two eutectics on either side of intermolecular complexes. The various thermodynamic parameters such as heat of mixing, entropy of fusion, roughness parameter, interfacial energy and excess thermodynamic functions of IMCs and eutectics were calculated using the heat of fusion values. The TGA and DTA studies were performed to understand the physico-chemical, thermal behavior and unique identity of newly synthesized organic complexes, 4-(dimethylamino)benzylidene-4-acetamideaniline (DMABPAA) and 4-(dimethylamino)benzylidene-4-nitroaniline (DMABPNA), and their respective enthalpy of fusion values were found to be 30.01 and 37.26 kJ mol− 1. The higher melting point of both the novel complexes than their parent’s compounds reveal the strong molecular interaction between parent components to yield the complex. The FTIR spectral analysis predicts the disappearance of aldehyde peaks of DMAB and NH2 peaks of PAA and PNA while the appearance of entirely new peaks than that of parent’s compounds are the supportive for the formation of new molecular entities. These findings are further supported by FTNMR spectrum studies by observation of disappearance of proton peak of aldehyde of DMAB and amine peaks of PAA and PNA rather formation of new imine proton peak or peaks were observed. The appearance of new peaks in Powder XRD of complexes than those of parent components is further indicative for the formation of complexes. The absorption spectrum of DMABPAA and DMABPNA showed intra-molecular charge-transfer (ICT) excited state absorption at 258 and 241 nm, respectively. Both the IMCs, DMABPAA and DMABPNA, show strong fluorescence with quantum yield 0.66 and 0.93, respectively, in methanol solution.