Tautomerism and IR spectroscopy of arylsulfonamides by quantum mechanical calculations.

The authors would like to acknowledge the contribution of the European COST Action CA17120 supported by the EU Framework Programme Horizon 2020, and thank the Computational Center of CSIC and Supercomputing Center Alhambra of UGR for the high-performance computing services, and Spanish projects FIS2016–77692-C2–2-P and PCIN-2017–098, and the Andalusian project P18-RT-3786 for financial support. A.P. de la Luz thanks to Secretaría de Educación, Ciencia, Tecnología e Innovación (SECTEI) of the Mexico City for the scholarship for the postdoctoral stay. The authors are grateful to the Dirección General de Cómputo y de Tecnologías de Información y Comunicación (DGCTIC) at the Universidad Nacional Autónoma de México (UNAM) for allocation of computer time in the supercomputer (Miztli, LANCAD-UNAM-DGTIC-203).The molecular structures of sulphonamides are interesting for evaluating their mobility in soils and preparing composite complexes for optimizing the use of these drugs. In this work, the molecular structures of several arylsulfonamides along with conformational analysis and tautomerism were investigated theoretically. The spectroscopical properties of several arylsulfonamides, were also studied at molecular level by using a computational modeling at quantum mechanics level. Besides, the controversial experimental results found in the infrared (IR) spectroscopy bands assignments of solid sulphonamides pushed us up to study computationally the crystal structure of sulfamethazine for clarifying previous assignment discrepancies. The previously proposed polymorphism in the crystal structure of this drug has been also clarified in this work.Dirección General de Cómputo y de Tecnologías de Información y ComunicaciónHorizon 2020 Framework ProgrammeEuropean Cooperation in Science and Technology CA17120Universidad Nacional Autónoma de México LANCAD-UNAM-DGTIC-203Universidad de Granada FIS2016–77692-C2–2-P, P18-RT-3786, PCIN-2017–09