CGRtools is an open-source Python library aimed to handle molecular and reaction information. It is the sole library developed so far which can process condensed graph of reaction (CGR) handling. CGR provides the possibility for advanced operations with reaction information and could be used for reaction descriptor calculation, structure−reactivity modeling, atom-to-atom mapping comparison and correction, reaction center extraction, reaction balancing, and some other related tasks. Unlike other popular libraries, CGRtools is fully written in Python with minor dependencies on other libraries and cross-platform. Reaction, molecule, and CGR objects in CGRtools support native Python methods and are comparable with the help of operations "equal to", "less than", and "bigger than". CGRtools supports common structural formats. CGRtools is distributed via an L-GPL license and available on https://github.com/cimmkzn/CGRtools.

In this paper, we compare the most popular Atom-to-Atom Mapping (AAM) tools: ChemAxon, [1] Indigo, [2] RDTool, [3] NameRXN (NextMove), [4] and RXNMapper [5] which implement different AAM algorithms. An open-source RDTool program was optimized, and its modified version ("new RDTool") was considered together with several consensus mapping strategies. The Condensed Graph of Reaction approach was used to calculate chemical distances and develop the "AAM fixer" algorithm for an automatized correction of erroneous mapping. The benchmarking calculations were performed on a Golden dataset containing 1851 manually mapped and curated reactions. The best performing RXNMapper program together with the AMM Fixer was applied to map the USPTO database. The Golden dataset, mapped USPTO and optimized RDTool are available in the GitHub repository https://github.com/Laboratoire-de-Chemoinformatique.

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Density-functional theory calculations of a series of organic biradicals on the basis of the N,N 0dioxy-2,6-diazaadamantane core with different substituents at carbon atoms adjacent to the nitroxyl groups have been performed by the UB3LYP/6-31111G(2d,2p) method. Using the breaking symmetry approach, the values of the exchange interaction parameter, J, between the radical centers are calculated. It is shown that the intramolecular exchange interaction for the most part is ferromagnetic in nature, but the J parameter gradually decreases, changing its sign to antiferromagnetic interaction for the last substituent in the following sequence:The calculations at the UHSEH1PBE/6-31111G (2d,2p) level with the most of substituents show nearly the same variation sequence for the J parameter. It is concluded that spin polarization effects in the diazaadamantane cage and a direct through-space antiferromagnetic exchange interaction between the nitroxyl groups are the main mechanisms contributing to the exchange interaction parameter value in the studied series of compounds. The exchange coupling constant, J, depends on the electronic effects and geometry of the substituents, as well as on their specific interactions with the nitroxyl radical groups. K E Y W O R D S broken symmetry approach, DFT, 2,6-diazaadamantane, exchange interaction, organic biradicals, open-shell systems | I N TR ODU C TI ONStable and persistent organic radicals have drawn much attention in recent years in connection with the design and preparation of purely organic magnetic materials exhibiting ferromagnetic, ferrimagnetic, or superparamagnetic properties. [1,2] Commonly, exchange interactions between freeradical centers which are present in this kind of materials cause these properties. First examples of purely organic ferromagnetic compounds were prepared in the early 1990s. [3,4] Since then, significant progress has been made in the area of purely organic magnets, including the report of dithiadiazolyl radicals showing remanent magnetization below 36 K. [5] So far, this is the highest Curie temperature recorded for organic radicals. An interesting case of combining the ferromagnetic exchange interaction between paramagnetic centers with second-order nonlinear optical responses is found theoretically in bis-TEMPO biradicals coupled through fluorescent protein chromophores. [6,7] Stable organic radicals are also of special interest in connection with the development of quantum computing [8][9][10] and molecular spintronics. [11] For example, information processing based on weakly exchange-coupled multispin systems is one of the promising directions in quantum computation technologies. [12] The design of stable multiradical organic materials, potentially applicable as quantum bits, can be carefully controlled by the use of modern quantum-chemical approaches. [13] Since Int J Quantum Chem. 2018;118:e25568.