High-Pressure Structural and Electronic Properties of Bibenzyl (1,2-Diphenylethane) from Synchrotron SC-XRD and Two-Photon-Induced Fluorescence

Year: 2026

Authors: Agati M., Romi S., Fanetti S., Garbarino G., Haines J., Bini R.

Autors Affiliation: LENS, European Lab Nonlinear Spect, I-50019 Sesto Fiorentino, Firenze, Italy; Univ Firenze, Dipartimento Chim Ugo Schiff, I-50019 Sesto Fiorentino, Italy; Ist Chim Composti OrganoMetall, ICCOM CNR, I-50019 Sesto Fiorentino, Firenze, Italy; European Synchrotron Radiat Facil ESRF, F-38043 Grenoble, France; Univ Montpellier, ICGM, UMR5253, CNRS,ENSCM, F-34293 Montpellier, France; Ist Nazl Ottica, INO CNR, I-50019 Florence, Italy.

Abstract: The structural and electronic properties of bibenzyl (1,2-diphenylethane) are investigated as a function of pressure using single-crystal X-ray diffraction (SC-XRD) and two-photon-induced fluorescence. Bibenzyl is an appealing pseudostilbene compound for the high-pressure synthesis of mixed carbon nanothreads with tunable optical properties, due to its fully saturated linking group. Crystal structures are refined from ambient pressure up to 37 GPa by synchrotron XRD, and the appearance of pseudosymmetry traits at 13 GPa reveals a phase transition that consists of molecular distortions leading to the tripling of the a axis and asymmetric unit while maintaining the unit cell’s point group symmetry. Two-photon-induced fluorescence up to 18 GPa provides insights into the structural changes where the strengthening of pi-pi interactions at the phase transition stabilizes the electronic ground state and drives the molecular distortions that occur at that pressure. Coupling structural and electronic properties rationalizes the high-pressure reactivity compared to other pseudostilbenes, showing that the molecular evolution from the added torsional degree of freedom and establishment of pi-pi interactions at the phase transition lead the molecular conformation to an unfavorable state for pressure-induced polymerization.

Journal/Review: CRYSTAL GROWTH & DESIGN

Volume: 26 (2)      Pages from: 970  to: 984

More Information: We acknowledge financial support under the National Recovery and Resilience Plan (NRRP), Mission 4, Component 2, Investment 1.1, Call for Tender No. 104, published on 2.2.2022 by the Italian Ministry of University and Research (MUR), funded by the European Union – NextGenerationEU – Project Title NEw MatErials by high-presSure chemIStry – CUP B53D23015760006 – Grant Assignment Decree No. 1064 adopted on 18/07/2023 by the Italian Ministry of University and Research(MUR). We acknowledge financial support from the integrated infrastructure initiative in photonic and quantum sciences I-PHOQS. We thank ESRF, the European synchrotron, f or hosting our experiment under proposal number CH-7235. We also thank Dominique Granier (Reseau Rayons X et gamma de l’Universite de Montpellier) for helping with in-house SC-XRD measurements.
KeyWords: Vibrational-spectra; Universal Equation; Crystal-structures; Bond-length; Stilbene; Phase; Raman; Temperature; Azobenzene; Emission
DOI: 10.1021/acs.cgd.5c01569