Conformational and NMR analysis on cis 1,3-indanediol

Ab initio and density functional theory (DFT) have been applied to study the conformational species of cis 1,3-indanediol. We found five quasi-degenerate conformational minima, which can interchange through the ring-puckering and the internal rotation of the OH groups on the five-membered ring. The intramolecular OH⋯π and OH⋯OH hydrogen bonding have been found of critical importance for the conformational stabilities. Using DFT methods, the relative stability ordering of cis 1,3-indanediol reveal the delicate basis set dependence. Furthermore, the order of stability of the conformers appears to be dependent of the calculation methods used (DFT and ab initio). Among five conformers of the cis 1,3-indanediol, there are four conformers possessing OH⋯π and/or OH⋯OH H-bonds. Finally, the chemical shifts of cis 1,3-indanediol have been calculated using Gauge-Independent Atomic Orbital (GIAO) method and obtained results have been compared with experimental data. Experimental 1H and 13C NMR spectra of the cis 1,3-indanediol were measured in DMSO-d6 solution. A complex consisting of two DMSO molecules connected with the cis 1,3-indanediol molecule by OH⋯OS(CH3)2 hydrogen bonds has been built and used for NMR calculations. Theoretical calculations predict a significant downfield shift for hydroxyl protons of cis 1,3-indanediol involved in intermolecular OH⋯DMSO hydrogen bonds.