Synthesis, crystal structure, and optical properties of fluorinated poly(pyrazole) ligands and in silico assessment of their affinity for volatile organic compounds. (8th April 2020)

• Record Type: Journal Article
• Authors: Pedrini, Alessandro; Maspero, Angelo; Bracco, Silvia; Comotti, Angelina; Galli, Simona; Marchiò, Luciano; Nardo, Luca; Penoni, Andrea; Scapinello, Luca; Sozzani, Piero; Vesco, Guglielmo; Mella, Massimo
• Is Part Of: New journal of chemistry. Volume 44:Number 16(2020)
• Page Start: 6443
• Page End: 6455
• Publication Date: 2020-04-08
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/d0nj00259c
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : Increasing fluorination of an organic ligand forming porous coordination polymers results in enhanced affinity for volatile organic compounds (VOCs) without affecting the fluorescence properties, thus opening new perspectives for VOC sensing. Abstract : Three new fluorinated bis(pyrazoles), namely: 1, 4-bis(1 H -pyrazol-4-ylethynyl)-2-fluorobenzene (H2 BPEFB ), 1, 4-bis(1 H -pyrazol-4-ylethynyl)-2, 3-difluorobenzene (H2 BPEF2 B ) and 1, 4-bis(1 H -pyrazol-4-ylethynyl)-tetrafluorobenzene (H2 BPEF4 B ), have been synthesized taking advantage of Sonogashira coupling reactions, and characterized as per their crystal and molecular structure, spectroscopic and dielectric properties, and hydrophobicity. In the crystal structures, the three molecules, whose deviation from planarity increases on increasing the fluorination degree, interact by means of hydrogen bonds, forming 2D supramolecular layers. Notably, the absorption and fluorescence emission properties are only slightly affected by the fluorination degree in both the solid state and solution. Furthermore, the spectral line-shapes are weakly dependent on the environment when dissolved in a number of solvents of different polarity and hydrogen-bonding affinity. On the other hand, the dielectric constant monotonically increases on increasing the number of fluorine atoms. In silico molecular modeling with time-dependent density functional theory has offered a valuable means to rationalize the above mentioned behaviors and has shed some light on the ligand affinity towards representative gases – H2 O and CO2 – and organic solvents – toluene.