Rotational Isomerism of an Amide Substituted Squaraine Dye: A Combined Spectroscopic and Computational Study

Quantum chemical package Jaguar: A survey of recent developments and unique features

This paper is dedicated to the quantum chemical package Jaguar, which is commercial software developed and distributed by Schrödinger, Inc. We discuss Jaguar's scientific features that are relevant to chemical research as well as describe those aspects of the program that are pertinent to the user interface, the organization of the computer code, and its maintenance and testing. Among the scientific topics that feature prominently in this paper are the quantum chemical methods grounded in the pseudospectral approach. A number of multistep workflows dependent on Jaguar are covered: prediction of protonation equilibria in aqueous solutions (particularly calculations of tautomeric stability and pKa), reactivity predictions based on automated transition state search, assembly of Boltzmann-averaged spectra such as vibrational and electronic circular dichroism, as well as nuclear magnetic resonance. Discussed also are quantum chemical calculations that are oriented toward materials science applications, in particular, prediction of properties of optoelectronic materials and organic semiconductors, and molecular catalyst design. The topic of treatment of conformations inevitably comes up in real world research projects and is considered as part of all the workflows mentioned above. In addition, we examine the role of machine learning methods in quantum chemical calculations performed by Jaguar, from auxiliary functions that return the approximate calculation runtime in a user interface, to prediction of actual molecular properties. The current work is second in a series of reviews of Jaguar, the first having been published more than ten years ago. Thus, this paper serves as a rare milestone on the path that is being traversed by Jaguar's development in more than thirty years of its existence.

Conformational and environmental effects on the electronic and vibrational properties of dyes for solar cell devices

The main challenge for solar cell devices is harvesting photons beyond the visible by reaching the red-edge (650-780 nm). Dye-sensitized solar cell (DSSC) devices combine the optical absorption and the charge separation processes by the association of a sensitizer as a light-absorbing material (dye molecules, whose absorption can be tuned and designed) with a wide band gap nanostructured semiconductor. Conformational and environmental effects (i.e., solvent, pH) can drastically influence the photophysical properties of molecular dyes. This study proposes a combined experimental and computational approach for the comprehensive investigation of the electronic and vibrational properties of a unique class of organic dye compounds belonging to the family of red-absorbing dyes, known as squaraines. Our focus lies on elucidating the intricate interplay between the molecular structure, vibrational dynamics, and optical properties of squaraines using state-of-the-art density functional theory calculations and spectroscopic techniques. Through systematic vibrational and optical analyses, we show that (i) the main absorption peak in the visible range is influenced by the conformational and protonation equilibria, (ii) the solvent polarity tunes the position of the UV-vis absorption, and (iii) the vibrational spectroscopy techniques (infrared and Raman) can be used as informative tools to distinguish between different conformations and protonation states. This comprehensive understanding offers valuable insights into the design and optimization of squaraine-based DSSCs for enhanced solar energy conversion efficiency.