Tautomerism and hydrogen bonding in guaninium phosphite and guaninium phosphate salts

Guanine-Stabilized Formamidinium Lead Iodide Perovskites

Formamidinium (FA) lead iodide perovskite materials feature promising photovoltaic performances and superior thermal stabilities. However, conversion of the perovskite α-FAPbI₃ phase to the thermodynamically stable yet photovoltaically inactive δ-FAPbI₃ phase compromises the photovoltaic performance. A strategy is presented to address this challenge by using low-dimensional hybrid perovskite materials comprising guaninium (G) organic spacer layers that act as stabilizers of the three-dimensional α-FAPbI₃ phase. The underlying mode of interaction at the atomic level is unraveled by means of solid-state nuclear magnetic resonance spectroscopy, X-ray crystallography, transmission electron microscopy, molecular dynamics simulations, and DFT calculations. Low-dimensional-phase-containing hybrid FAPbI₃ perovskite solar cells are obtained with improved performance and enhanced long-term stability.

Molecular tapes in the structure of isoguaninium chloride

Isoguanine, an analogue of guanine, is of intrinsic interest as a noncanonical nucleobase. The crystal structure of isoguaninium chloride (systematic name: 6-amino-2-oxo-1H,7H-purin-3-ium chloride), C₅H₆N₅O⁺·Cl^-, has been determined by single-crystal X-ray diffraction. Structure analysis was supported by electrostatic interaction energy (E_es) calculations based on charge density reconstructed with the UBDB databank. In the structure, two kinds of molecular tapes are observed, one parallel to (010) and the other parallel to (50-4). The tapes are formed by dimers of isoguaninium cations interacting with chloride anions. E_es analysis indicates that cations in one kind of tape are oriented so as to minimize repulsive electrostatic interactions.

Co-crystallisation of cytosine with 1,10-phenanthroline: computational screening and experimental realisation

Crystal structure prediction calculations applied to co-crystals of 1,10-phenanthroline and nucleobases (A, T, C, G) show that only cytosine is expected to form a 1 : 1 co-crystal. Experiments provide verification for this result although the observed co-crystal crystallises with Z′ = 2, not Z′ = 1.