Structural and spectroscopic properties of posaconazole – Experimental and theoretical studies

Abstract

The paper compares the experimental FT-IR, UV–vis and 1H NMR spectra of posaconazole with the DFT calculations using five different functionals. The results were compared with previously reported data related to its analogue – itraconazole. Owing to the lack of crystallographic data, the IR analysis for posaconazole was performed for the rotamer optimized at the B3LYP/6-311++G(d,p) level of theory. This analysis shows good accordance with the experimental IR spectrum. The best compatibility between the experimental and theoretical UV spectra was observed with the use of CAM-B3LYP/6-31G(d,p) method for both conazoles. The reason for the difference in the UV–vis spectra of posaconazole and itraconazole was discussed based on linear response time-dependent DFT and natural bond orbital methods. The calculated 1H NMR spectrum shows that the DFT formalism, particularly the B3LYP functional, gives an accurate description of the posaconazole chemical shifts.