Sadhan Basu

Bio: Sadhan Basu is an academic researcher from University of Calcutta. The author has contributed to research in topics: Free electron model & Absorption spectroscopy. The author has an hindex of 12, co-authored 77 publications receiving 614 citations.

Theory of Solvent Effects on Molecular Electronic Spectra

Abstract: Publisher Summary This chapter provides a detailed quantum mechanical discussion of the problem in terms of second-order perturbation theory. The frequency of a molecular electronic absorption band is generally displaced when a molecule is immersed in a solvent medium such as a liquid or a foreign gas. These shifts are usually towards longer wavelengths although the opposite is sometimes true. In the recent years, considerable progress is made in understanding the effect of solvent on various spectral characteristics of a solute using quantum mechanical methods. When a molecule absorbs or emits light undergoing an electronic transition from one state to another, it is important to realize that both the energy and the electronic charge distribution in the molecule change. The calculation of stabilization energy of an electronic state due to solvent-solute interaction was first made by Ooshika using quantum mechanical perturbation theory. The same quantum mechanical formulation was used by Longuet–Higgins and Pople and by McRae.

Crystal spectra of metal chelates—I

Abstract: From the measurement of absorption spectra of crystals of biguanide complexes of copper chloride, -bromide and -fluoride, it has been concluded that the five fold degenerate d -orbitals of copper ion are split into four levels by the electrostatic field of the four ligand donor atoms in the plane of the molecule. The electronic transitions between these levels give rise to three absorption bands two of which are both x ( y ) and z polarized, while the other is only x ( y ) polarized. The vibronic perturbation which makes these forbidden g-g transitions allowed has been assigned. Similar effect has been noticed with nickel complex, but the analysis was not complete as the whole of the spectrum could not be recorded.

The Halogen Bond

Abstract: The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

Polarizable continuum model

Abstract: The polarizable continuum model (PCM) is a computational method originally formulated 30 years ago but still today it represents one of the most successful examples among continuum solvation models. Such a success is mainly because of the continuous improvements, both in terms of computational efficiency and generality, made by all the people involved in the PCM project. The result of these efforts is that nowadays, PCM, with all its different variants, is the default choice in many computational codes to couple a quantum–mechanical (QM) description of a molecular system with a continuum description of the environment. In this review, a brief presentation of the main methodological and computational aspects of the method will be given together with an analysis of strengths and critical issues of its coupling with different QM methods. Finally, some examples of applications will be presented and discussed to show the potentialities of PCM in describing the effects of environments of increasing complexity. © 2012 John Wiley & Sons, Ltd.

Invited review solvatochromic shifts: The influence of the medium on the energy of electronic states

Abstract: The displacement of electronic absorption and luminescence spectra (solvatochromic shifts) are related to the solute—medium interactions. These interactions can be non-specific (dielectric interactions) when they depend only on multiple and polarizability properties of the solute and solvent molecules; but specific associations such as hydrogen bonding can also be important. A number of examples of solvatochromic shifts are shown and discussed according to the various solute—medium interactions. The properties of solvent mixtures and those of rigid media are considered, as well as the “thermochromic shifts” which result from the change in the temperature of the medium. The use of solvatochromic shifts for the determination of the dipole moment and of the polarizability of electronically excited molecules has been important for an understanding of electron distribution changes in such states; examples of such determinations are given, together with references to the original literature. In the final section some limitations of the theories of solvent shifts and possible improvements are discussed.