Proceedings of the Indian Academy of Sciences - Chemical Sciences

1. Roozeboom’s melting point-composition diagrams have been prepared for the camphor-β-sulphonates (d anddl) ofo-,m- andp-chloraniline and camphor-β-sulphonyl-o-,m- andp-chlorophenylamides (d anddl). Three curves were obtained in each case which showed that they were truedl compounds. 2. A freezing-point equation has been developed. The above mentioned Roozeboom curves have been discussed in relation to the ideal case as given by this equation. It is found that the systems represented by these curves are complicated as their behaviour is not sufficiently understood. 3. The stability of these compounds has been discussed with the aid of Roozeboom’s melting-point diagrams. 4. The existence of racemates in solid, liquid and gaseous states has been discussed.

A large variety of molecular ferromagnets have been synthesized since the discovery of the first organic ferromagnets, including pure organic compounds, organometallic charge-transfer complexes, metal complex-organic radical compounds, and transition metal complexes coupled to organic radicals. Besides, there are many reports on the observation of ferromagnetism in polymers and organic matrix composites. Molecular ferromagnets have great potential in different areas of technology such as low frequency magnetic shielding, magnetic imaging, magneto-optics and information storage. We provide a brief review on the current strategies for the design of molecular (organic) ferromagnets. This includes exploiting the inherent advantages of molecular systems, such as the ability to fine-tune the properties at the molecular level, and to control dimensionality, supramolecular structuring and hierarchy of spin interactions etc. for carrying out structural modifications and chemical functionalisations of stable open-shell molecules in order to generate supramolecular structures in which the natural prediction for antiparallel spin alignment (antiferromagnetism) is avoided.

A new and elegant method, based on group theory, has been given for obtaining the maximum number of force constants needed in expressing the potential energy of a vibrating molecule characterised by a certain point group symmetry.

Novel tricyclic thienopyrimidines (3, 5, 6, 9, 11, 12) and triazole fused tetracyclic thienopyrimidines (4a-c, 10a-c) were synthesized from precursors 2-amino-6-methyl-4,5,6,7-tetrahydro-1-benzothiophene-3-carbonitrile 1 and 2-amino-7-oxo-4,5,6,7-tetrahydro-1-benzothio-phene-3-carbonitrile 7 respectively. The corresponding precursors were prepared by employing the Gewald reaction. The structures of newly synthesized compounds were characterized by spectral and analytical data. All the compounds were screened for their biological activities. Some of the compounds displayed promising antibacterial and antifungal activities.

Influence of the nature of support on the formation of catalytically active species was investigated to clarify the key factor for the synthesis of supported ammonium salt of 12-molybdophosphoric acid (AMPA) catalyst which maintains the activity of ammoxidation during 2-methylpyrazine reaction. With this aim, different loadings of niobia-, silica- and alumina-, supported AMPA catalysts were prepared. The AMPA loading was varied in the range of 5–25 wt%. The synthesized solids were characterized by nitrogen adsorption for BET surface area, XRD and 31P MAS NMR techniques. All the AMPA-supported samples are poorly crystalline even after 25 wt% AMPA loading. Investigations using 31P MAS NMR spectroscopy of samples revealed that Keggin ion existed as at least five different species on the supports. The investigated properties were acidity of the support and amount of AMPA loading on the support. Active sites for the ammoxidation of MP on supported AMPA catalysts seem to be the interacted and/or the lacunary species. Maximum catalytic activity could be obtained at lower loadings with AMPA deposited on acidic supports whereas the less acidic supports require higher loading. It was found that in order to efficiently generate the active interactive species, the support must have an acidity which promotes the formation of support-AMPA interactive species. It is possible to enhance the catalytic activity of the supported AMPA catalyst for ammoxidation of 2-methylpyrazine by controlling the acidity of the support and AMPA loading on the support.

A series of complex with a general formula of M(Fc2Ph2P) [Fc2Ph2P = 5,10-bisferrocenyl-15,20-bisphenylporphyrin (2 −); M = Fe(III)Cl Fe(III)(ClO4) and Cu(II)] have been synthesized and characterized. The single crystal X-ray structure of Cu II(Fc2Ph2P) has been reported in which two ferrocene moieties are in anti form with respect to each other. The ferrocenyl groups of Cu II(Fc2Ph2P) are more easily oxidized via a single two-electron quasi-reversible process compared to the free base ligand in which two 1e-oxidative response separated by 0.23 V are observed. Electrochemical study of FeIII(Fc2Ph2P)Cl revealed ferrocene-based two-electron quasi-reversible oxidation at 0.72 V indicating no observable coupling of the ferrocene moieties. The higher oxidation state of Fe(III) reduces the electron releasing tendency of the porphyrin ring and thus make the ferrocene oxidation difficult. The porphyrin, however, lack substituents at the β-pyrrolic positions, and the ferrocenyl moieties are therefore free to rotate. The observed electrochemical analyses thus demonstrate that the oxidation of the ferrocene subunit is strongly affected by porphyrin ring as well as the central metal through extended π-conjugation.

In this paper, we explore the catalytic activity of $$\hbox {SiO}_{{2}}$$ nanoparticles (NPs) as an eco-friendly, efficient and reusable catalyst in the synthesis of 2,3-dihydro-1H-perimidines as well as tetraketones. For tetraketones syntheses, a simple tandem Knoevenagel condensation following Michael addition procedure is performed by the reaction between benzaldehydes and 5,5-dimethyl-1,3-cyclohexanediones under solvent-free condition using $$\hbox {SiO}_{{2}}$$ NPs as an efficient solid catalyst. In addition, for 2,3-dihydro-1H-perimidines syntheses, cyclocondensation of various aldehydes with 1,8-diaminonaphthalene is achieved under solvent-free condition using $$\hbox {SiO}_{{2}}$$ NPs as a catalyst at room temperature. The results showed catalytic enhancement in both synthetic procedures. In this work, 4-(2,3-dihydro-1H-perimidin-2-yl)benzonitrile and 2-(pyridin-4-yl)-2,3-dihydro-1H-perimidine are synthesized as new compounds. Also, reusability study of $$\hbox {SiO}_{{2}}$$ NPs was done to ensure its applicability as a recycled catalyst in this work.   The catalytic activity of $$\hbox {SiO}_{{2}}$$ nanoparticles (NPs) as an eco-friendly, efficient and reusable catalyst in the synthesis of 2,3-dihydro-1H-perimidines as well as tetraketones is explored. For tetraketones syntheses, a simple tandem Knoevenagel condensation following Michael addition procedure is performed by the reaction between benzaldehydes and 5,5-dimethyl-1,3-cyclohexanediones under solvent-free condition using $$\hbox {SiO}_{{2}}$$ NPs as an efficient solid catalyst.

The kinetics of the hydrolysis of ethyl acetate in acetone-water and dioxane-water systems are reported. The rate constant passes through a minimum when the concentration of the organic solvent in the medium is in the neighbourhood of 80%. The temperature variation conforms strictly to the Arrhenius equation even for media containing extremely high proportions of organic solvent. Even though the activation energy is affected by changes in solvent composition, the variations are not sufficiently marked for an analysis. The frequency factor has got a tendency to follow the trend of activation energies.

9-Aminobenzanthrone, which has been prepared earlier by a tedious synthesis, has now been prepared from 3-bromobenzanthrone by nitration to 3-bromo-9-nitrobenzanthrone, reduction of the nitro derivative to 3-bromo-9-aminobenzanthrone, and debromination of the latter compound by palladium and hydrazine. 3∶12-Diaminodibenzanthrone (VIII) was formed as a minor product in the debromination. While the angular orientation of the fused pyridine ring in benzanthronequinoline, a product obtained by the action of glycerine and sulphuric acid on 2-aminoanthraquinone, has been established, the relative positions of the benzene and pyridine rings has not been proved so far. The Skraup reaction on 9-aminobenzanthrone gave benzanthronequinoline, thus proving its constitution as (IV). Cyananthrene, a vat dye obtained by alkali fusion of benzanthronequinoline, is therefore constituted as (X), and not as (IX) as sometimes stated in the literature.