Unveiling n → π* interactions: convergence of quantum crystallography and computational insights

Polo, Alvaro ; García-Orduña, Pilar ; Echeverría, Jorge ; Sanz Miguel, Pablo J. (Universidad de Zaragoza)

Resumen: We report the identification and characterization of a n → π* interaction between halide anions and a cationic purine nucleobase. Through a combined quantum crystallographic and computational approach, we demonstrate that perpendicular anion⋯(sp2)carbon contacts occur consistently at the C2 position of the purine nucleobase, with geometries and energies comparable to hydrogen bonds. High-resolution X-ray charge density analysis of 2[Br]·H2O confirms the existence of a bond path and an electron density depletion on C2, supporting a charge-transfer interaction. Complementary theoretical studies reveal a lone pair-to-π* orbital delocalization mechanism, with second-order NBO energies up to 6 kcal mol−1. The interaction persists with various anions, hydration levels, and C2 substitutions, highlighting its robustness and potential relevance in supramolecular chemistry. This study provides the experimental validation of an n → π* contact, supported by topological and electrostatic descriptors.

Idioma: Inglés

DOI: 10.1039/d5dt02386f

Año: 2026

Publicado en: Dalton Transactions (2026), [8 p.]
ISSN: 1477-9226

Financiación: info:eu-repo/grantAgreement/ES/DGA/E05-23R
Financiación: info:eu-repo/grantAgreement/ES/DGA/E42-23R
Financiación: info:eu-repo/grantAgreement/ES/MCIU-AEI-FEDER/PID2021-122406NB-I00

Tipo y forma: Article (Published version)

Área (Departamento): Área Química Inorgánica (Dpto. Química Inorgánica)