# A combined TD-DFT and spectroscopic investigation of the solute-solvent interactions of efavirenz.
> エファビレンツの溶質-溶媒相互作用に関するTD-DFTおよび分光学的解析


## Abstract

This study examined the solute-solvent interactions of efavirenz, a first-line antiretroviral agent for HIV/AIDS, whose clinical utility is limited by poor aqueous solubility. Using UV-visible spectrophotometry, proton NMR spectroscopy, and time-dependent density functional theory (TD-DFT) calculations, the spectral behavior of efavirenz was characterized across solvents of varying polarity. Two principal UV absorption bands were identified at 246–260 nm (band I) and 291–295 nm (band II). A bathochromic shift of approximately 13.69 nm in band I and a smaller bathochromic and hyperchromic shift in band II were recorded upon moving from cyclohexane to DMSO. These shifts are attributed to charge-transfer effects and intra- and intermolecular hydrogen bonding involving the amino (NH) and carbonyl (CO) groups. In NMR experiments, aromatic and amine protons exhibited greater deshielding in DMSO-d6 compared with CDCl3, consistent with increased delocalization of lone-pair electrons on the amino nitrogen in higher-polarity environments. TD-DFT-derived theoretical spectra showed strong concordance with experimental observations.

### Mechanism

The amino (NH) and carbonyl (CO) functional groups of efavirenz drive charge-transfer and intra-/intermolecular hydrogen bonding, producing bathochromic UV shifts and increased NMR deshielding as solvent polarity increases due to enhanced lone-pair electron delocalization on the amino nitrogen.

## Bibliographic

- **Authors**: Jordaan MA, Singh P, Martincigh BS
- **Journal**: Spectrochim Acta A Mol Biomol Spectrosc
- **Year**: 2016 (2016-03-15)
- **PMID**: [26773263](https://pubmed.ncbi.nlm.nih.gov/26773263/)
- **DOI**: [10.1016/j.saa.2015.12.008](https://doi.org/10.1016/j.saa.2015.12.008)
- **Study type**: other
- **Delivery route**: not specified
- **Effect reported**: not assessed

## Delivery context

The delivery route is not clearly identifiable from this paper. For hydrogen intake, inhalation is the most efficient route; inhalation, however, carries explosion risk (empirical LFL of 10%; high-concentration devices are not recommended).

## Safety notes

The delivery route is not clearly identifiable from this paper. For hydrogen intake, inhalation is the most efficient route; inhalation, however, carries explosion risk (empirical LFL of 10%; high-concentration devices are not recommended).

See also:
- [Inhalation concentration and LFL / UFL](https://h2-papers.org/en/safety-notes/inhalation-concentration)
- [Consumer Affairs Agency accident cases](https://h2-papers.org/en/safety-notes/accident-cases)

---

> **Cite as**: H2 Papers — PMID 26773263. https://h2-papers.org/en/papers/26773263
> **Source**: PubMed PMID [26773263](https://pubmed.ncbi.nlm.nih.gov/26773263/)