The charge transfer (CT) interaction between two fused heterocyclic compounds with basic pyrrole group as donors, viz., indole (IND) and carbazole (CAR), and iodine (acceptor) in DMSO medium is investigated by ultrasonic and UV-Visible spectral methods at 303 K. The formation of CT complex in these systems is established from the trend in acoustical and excess thermo acoustical properties with molar concentration. The frequency acoustic spectra (FAS) is also carried out on these two systems for two fixed concentrations 0.002 M and 0.02 M, and in the frequency range 1 MHz-10 MHz to justify the frequency chosen for ultrasonic study. The absorption coefficient values in solution are computed and discussed. The formation constants of these complexes are determined using Kannappan equation in ultrasonic method. The formation of 1:1 complexes between iodine and IND, CAR was established by the theory of Benesi - Hildebrand in the UV-visible spectroscopic method. The stability constants of the CT complexes determined by spectroscopic and ultrasonic methods show a similar trend. These values also indicate that the presence of fused aromatic ring influences significantly when compared with K values of similar CT complexes of parent five membered heterocyclic compound (pyrrole) reported by us earlier. (C) 2017 Elsevier B.V. All rights reserved.

Ultrasonic investigation has been carried out on five binary and four ternary liquid mixtures to identify the dominance of solute-solute interactions. p-Chloranil is used as acceptor and four aromatic amines are used as donors. Primary, secondary and tertiary amines were used mainly to determine the difference in the site of complex formation. The study was made in DMSO at 303 K and at atmospheric pressure. The trend in acoustical and excess thermo acoustical parameters of mixtures containing p-chloranil and amines is used to identify the existence of intermolecular interaction, probably through hydrogen bonded or charge transfer complex formation. The formation of 1:1 complexes between p-chloranil and aromatic amines was established by UV-visible spectroscopic methods at 303 K. The formation constants of the charge transfer complexes were computed by spectroscopic and ultrasonic methods which show similar trends and well establish the influence of structural aspect of the amine (donor) on the stability of charge transfer complexes. (C) 2013 Elsevier BM. All rights reserved.

The thermodynamic stability of complexes formed between N,N-dimethylaniline (DMANI) and three ketones, namely, acetophenone (ACP), 4-chloroactophenone (ClACP) and 4-methylacetophenone (MACP) in n-hexane is extensively investigated by spectral and ultrasonic methods. The ultrasound scan was carried out in the temperature range 208.15-313.15 K and at atmospheric pressure on solutions containing equimolar concentrations of components ranging from 0.025 to 0.2 M. The existence of solute-solute interactions has also been confirmed through electronic absorption spectra analyzed with Benesi-Hildebrand theory at 303.15 K. The stability constants of the donor-acceptor complexes determined both by spectroscopic and ultrasonic methods are comparable and follow similar trends. The trend in the formation constants is discussed with structures of the components. The thermodynamic behavior of the systems was explained through the computed values of the free energy (Delta G), enthalpy (Delta H) and entropy (Delta S) changes for complex formation are computed and discussed. (C) 2012 Elsevier B.V. All rights reserved.

The results of a new experimental study of thermo physical properties for eight binary systems of cinnamaldehyde with different alkanols have been presented. Speed of ultrasound (u), density (rho) and viscosity (eta) at 303.15 K and atmospheric pressure have been measured over the whole range of composition. These properties have been used to calculate various thermo acoustical parameters. The variations in these parameters have been studied in terms of nature and extent of interaction and the effect of structure of alcohols on the existing interactions. The non-ideal behaviour of the binary systems has been revealed through the sign and magnitude of excess velocity, viscosity deviation and other excess parameters. These parameters have been studied on the basis of dipole-dipole interactions and hydrogen bonding. The excess parameters have been fitted to polynomial type Redlich-Kister equation and the coefficients of the fitting have been found to support the present investigation.

Ultrasonic investigation has been carried out on six ternary systems to establish the complex formation between p-chloranil (acceptor) and six aromatic hydrocarbons (donors), namely, benzene, toluene, o-xylene, m-xylene, p-xylene and mesitylene in DMSO medium at 303.15 K and at atmospheric pressure. Studies were carried out in the concentration range of 0.002 to 0.02 M of acceptor and donor with equimolar concentration of the two components in solution. The trend in the acoustical parameters and magnitude of excess thermo acoustical parameters has been used to identify the existence of strong intermolecular interaction through charge transfer complex formation. The formation of 1:1 complex was also confirmed by UV–Visible spectroscopic method at 303.15 K in these systems. It may be pointed out that the formation constants of the charge transfer complexes determined by Benesi–Hildebrand (spectroscopic) and Kannappan (ultrasonic) methods show similar trend and well establish the influence of structural aspect of the donor aromatic compounds on the stability of charge transfer complexes.

Ultrasonic velocity (u), density (rho) and coefficient of viscosity (eta) were measured for ternary mixtures containing aniline (ANI) as common component and acetophenone (ACP), 4-chloroactophenone (CIACP) and 4-methylacetophenone (MACP) as other components in n-hexane medium in the concentration range 0.025-0.2 M. The measurements were made at four different temperatures, namely, 293, 298, 303 and 308 K and at atmospheric pressure. The experimental results have been used to calculate various acoustical parameters and excess parameters. The trend in these parameters with concentration establishes that (i) strong intermolecular interactions exist in these mixtures and (ii) formation of charge transfer complexes through hydrogen bonding between primary amine and aromatic ketones. The formation of complexes has also been confirmed by optical spectroscopy at 303 K. The formation constants of the charge transfer complexes determined using Benesi-Hildebrand equation (spectroscopic method) are comparable with those obtained using Kannappan equation (ultrasonic method). It is observed that the stability of the complexes is influenced by the structure of the component molecules. In order to assess the thermodynamic stability of the complexes, free energy of formation (Delta G), enthalpy of formation (Delta H) and entropy changes (Delta S) are computed. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.

The FTIR spectrum of 2-nitroaniline was recorded in the regions 4000-400 cm(-1). The optimized molecular geometry, bond orders, atomic charges, harmonic vibrational wave numbers and intensities of vibrational bands of 2-nitroaniline and its cation were calculated at DFT levels invoking two different basis sets 6-31G** and 6-31+G** using Gaussian 03W program. The X-ray geometry and FTIR vibrational frequencies were compared with the results of DFT calculations. The thermal stability of 2NA is studied by the thermo gravimetric analysis (TGA). Experimental degradation process of 2-nitroaniline was interpreted with the bond order analysis. The Mulliken atomic charge analysis was also made in the present study. Based on the molecular geometry and Mulliken charge analysis, intra molecular hydrogen bonding was identified.

It is an attempt to explain a physiological phenomenon, hypoglycemic effect, on the basis of molecular interactions through physical parameters in human mixtard insulin–doxycycline hyclate system. The degree of potentiation of insulin hypoglycemia is higher with doxycycline. The molecular basis of interaction of doxycycline hyclate and human mixtard insulin is attempted in aqueous environment through dilute solution viscometric, ultrasonic and refractometric techniques at physiological temperatures. The viscometric parameters establish the doxycycline–insulin interactions. The solute–solute interactions have been established through the linear behaviour of ultrasonic velocity and related parameters. The refractive indices indicate the chemical nature of blend solutions of doxycycline hyclate and human mixtard insulin.

Charge-transfer complexes formed between iodine (σ-acceptor) and pyrrole, thiophene and pyridine (π as well as n-electron donors) have been studied spectrophotometric and ultrasonic techniques at 303.15 K in dimethyl sulphoxide medium. The measured values of ultrasonic velocity, density and viscosity and the derived acoustical parameters such as adiabatic compressibility (κ), free length (Lf), internal pressure (πi), molar volume (Vm) and available volume (Va) have been used to study the molecular interactions and the complexes of heterocyclic aromatic compounds. The excess thermodynamic parameters like excess velocity (uE), excess adiabatic compressibility (κE), excess free length (LfE), excess molar volume (VmE) and excess available volume (VaE) have been computed and the sign and magnitude of these parameters indicate the strength of interactions and the formation of charge-transfer complex. The formation constants of the charge-transfer complexes were determined by the Benesi–Hildebrand equations (optical method) and compared with those obtained from Kannappan method (ultrasonic method). The formation constants of complexes of iodine with aromatic compounds depend on the structure of the donor and acceptor molecules.

The acoustical parameters for two binary liquid mixtures namely, acetone-carbon tetrachloride (CCl4) and acetone benzene have been determined at three different temperatures. The acoustical parameters such as the adiabatic compressibility kappa, the free length of interaction L-f, interaction parameter chi, Lennard Jones Potential (LJP) and also excess parameters such as excess velocity u(E), excess compressibility K-E, excess volume V-f(E) and excess free length L-f(E) are computed for the two systems at 303K, 308K and 313K from the measured ultrasonic velocity and density values. The extent of interactions existing between component molecules has been found out. In acetone - CCl4 System, the interaction parameter values have been out to be negative suggesting the presence of weak dipole -induced dipole interactions in this system. However, in acetone - benzene system, there are strong dipole - induced dipole interactions. With increase in temperature, the extent of interaction becomes weak in both the systems due to thermal agitation of the component molecules.

The ultrasonic velocities were measured in binary mixtures of o-cresol, p-cresol, o-chlorophenol and p-chlorophenol with CCl4 at 303,15 K. The relative merits of Nomoto's theory, Van Deal and Vangeel ideal mixing relation, free length theory and collision factor theory in the binary liquid mixtures are compared. The values of molecular interaction term a for the liquid mixtures are used to understand the molecular interactions.