Mapping the Interaction\nLandscape of Adenosine and\nMinoxidil Sulfate Using an Independent Gradient Model Based on Hirshfeld\nPartition and Interaction Region Indicator

Using theoretical techniques, the\ninteractions between adenosine\n(AD) and minoxidil sulfate (MS) were studied using the DFT/M06-2X/aug-cc-pVDZ\nlevel of theory. The formation of the complex was thermodynamically\nfavorable, so we carried out further studies. Frontier molecular orbital\nanalysis shows that the HOMO–LUMO– gap is high (6.81\neV), which means that the complex is kinetically stable. The global\nreactivity parameters were also calculated to get insight about the\nchemical reactivity of the complex. Molecular electrostatic potential\nand charge analyses were carried out for the optimized complex. To\nstudy the charge transfer and inter- and intramolecular interactions\npresent in the complex molecule, we employed natural bond orbital\nanalysis. Noncovalent interaction (NCI) analysis along with IGMH and\nIRI analyses further helped us find the weak interactions. The presence\nof hydrogen bonds between the N atom (N<sub>27</sub>) of MS and H\natom (H<sub>66</sub>) of AD and O atom (O<sub>32</sub>) of MS and\nH atom (H<sub>46</sub>) of AD was the main finding of these analyses.\nQTAIM investigation also supports this finding. EDA analysis was carried\nout to further study the intermolecular interactions present within\nthe complex. Thus, the present investigation unveils the existence\nof weak NCIs in the complex.