Towards molecular alloys: computational and experimental studies on ( p -NCC 6 F 4 CNSeSeN) x ( p -NCC 6 F 4 CNSSN) 1- x

• Published in: Physical chemistry chemical physics : PCCP 2024-04, Vol.26 (15), p.12097-12106
• Main Authors: Wehelie, Asli M, Watanabe, Lara K, Zhang, Bin, Nikoo, Sahar, Rawson, Jeremy M
• Format: Article
• Language: English
• Subjects: Antiferromagnetism; Charge distribution; Crystallization; Crystallography; Diamagnetism; Dichloromethane; Evaporation; Phase separation; Radicals; Recrystallization; Selenium; Sublimation; X ray powder diffraction; X-ray diffraction
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d4cp00188e

The β-phase of the radical -NCC F CNSSN (1β) crystallizes in the orthorhombic space group d 2 and orders as a canted antiferromagnet with = 36 K. Computational studies (B3LYP or M06-2X functional with the cc-pVTZ-PP(-F)+basis set) of the microscopic nearest-neighbour magnetic exchange coupling in 1β and in the hypothetical isomorphous phase of the selenium radical -NCC F CNSeSeN (2β) revealed that replacement of S by Se should lead to a significant enhancement in the magnetic ordering temperature by 20% (B3LYP) - 30% (M06-2X). Recrystallization of 2 from solution or vacuum sublimation afforded only the known diamagnetic, dimeric phase, 2α. Computational studies indicated that both the molecular geometry and charge distribution for 1 and 2 are extremely similar and experimental approaches to form alloys of the general form 1 2 were explored: attempts to cosublime 1 and 2 were unsuccessful, forming only 1β due to the low volatility of 2. Crystallization of pure 1 by solution evaporation was found to afford polymorph 1α (triclinic, 1̄) selectively, irrespective of the solvent employed (CH Cl , MeCN, PhMe or THF) but 1α transformed to 1β upon subsequent vacuum sublimation. Crystallization of 1 in the presence of 2 (up to 20 mol%) from solution evaporation was examined. At 20 mol% there was clear evidence for formation of both 1α and 2α as distinct crystallographic phases by powder X-ray diffraction (PXRD) but some evidence for doping of 2 into 1α at low concentration (≤15 mol percent) was observed. Attempts to sublime a sample of 1 2 led to phase separation with the isolation of needle-shaped crystals of pure 1β characterized by X-ray diffraction.