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The ongoing integration of quantum chemistry, statistical mechanics, and artificial intelligence is paving the route toward more effective and accurate strategies for the investigation of the spectroscopic properties of medium-to-large size chromo- phores in condensed phases. In this context we are developing a novel workflow aimed at improving the generality, reliability, and ease of use of the available computational tools. In this paper we report our latest developments with specific reference to unsupervised atomistic simulations employing non periodic boundary conditions (NPBC) followed by clustering of the trajectories employing optimized feature spaces. Next accurate variational computations are performed for a representative point of each cluster, whereas intracluster fluctuations are taken into account by a cheap yet reliable perturbative approach. A number of methodological improvements have been introduced including, e.g., more realistic reaction field effects at the outer boundary of the simulation sphere, automatic definition of the feature space by continuous perception of solute−solvent interactions, full account of polarization and charge transfer in the first solvation shell, and inclusion of vibronic contributions. After its validation, this new approach has been applied to the challenging case of solvatochromic effects on the UV−vis spectra of a prototypical nitroxide radical (TEMPO) in different solvents. The reliability, effectiveness, and robustness of the new platform is demonstrated by the remarkable agreement with experiment of the results obtained through an unsupervised approach characterized by a strongly reduced computational cost as compared to that of conventional quantum mechanics and molecular mechanics models without any accuracy reduction.

The classical modelling of organic molecules is based on force fields of commercial standard libraries, which might be limited and can be potentially inaccurate for compounds outside the data set. One common solution to this is the derivation of ad-hoc force field parameters for new molecules. However, this approach might be long and expensive even for experienced chemist. In this prospective, we propose an integrated and automated toolkit, called SmartField, to obtain intra- and intermolecular force field parameters with a good degree of accuracy and a margin of transferability. SmartField extracts all bonded parameters directly from the quantum mechanical Hessian, while CM5 charge, and Lennard-Jones parameter are retrived from standard outputs. We assessed the accuracy of SmartField by comparing vibrational frequencies and geometries of data set of rigid and flexible compounds with their quantum counterpart. Furthermore, SmartField parameters are employed for the computation of the absorption and emission spectra of the indole moiety, and tryptophan amino acid, in water. A direct comparison with the available experimental data is good and it gives a support of SmartField-derived force fields, which can be exploited for the modelling of novel and more complex compounds.

Methyllithium (MeLi) is the parent archetypal organolithium complex. MeLi exists as aggregates in solutions and solid states. Monomeric MeLi is postulated as a highly reactive intermediate and plays a vital role in understanding MeLi-mediated reactions but has not been isolated. Herein, we report the synthesis and structure of the first monomeric MeLi complex enabled by a new hexadentate neutral amine ligand.