Decorating BODIPY with Electron‐Withdrawing NO Group: Spectroelectrochemical Consequences and Computational Investigation. Issue 15 (5th August 2021)

• Record Type: Journal Article
• Authors: Silva, Thaissa L.; Do Nascimento, Tamires A.; De Almeida, Andresa K. A.; Melo, Shaiani M. G.; Da Silva, Julio C. S.; Xavier, Jadriane A.; Xavier, André F. A.; Santos, Danyelle C.; Wadhawan, Jay; Emery, Flavio S.; Goulart, Marilia O. F.
• Is Part Of: ChemElectroChem. Volume 8:Issue 15(2021)
• Page Start: 2921
• Page End: 2934
• Publication Date: 2021-08-05
• Subjects: electroreduction -- electrooxidation -- substituent effects -- spectroelectrochemistry -- weak interactions; Electrochemistry -- Periodicals; 541.37
• DOI: 10.1002/celc.202100609
• Languages: English
• ISSNs: 2196-0216

Abstract

Abstract: 4, 4‐difluoro‐5, 7‐dimethyl‐4‐bora‐3a, 4a‐diaza‐s‐indacene (BODIPY) and derivatives are an outstanding class of fluorescent dyes. Herein, we report on the introduction of a nitrosyl moiety into the BODIPY structure and its dramatic effect on the observed electrochemical reaction mechanism. 6‐Nitrosyl‐8‐phenyl‐BODIPY and its 5‐nitrosyl positional isomer, compounds 2 and 3, respectively, were obtained from the meso precursor, 8‐phenyl‐BODIPY (1 ), by nitrosation. Electrochemical studies for 1 –3 are reported. Cyclic voltammetry and differential pulse voltammetry in degassed DMF or in MeCN (reduction+oxidation), both with n ‐Bu4 NPF6 (0.1 mol L −1 ), were obtained. Compound 1 displays the usual behaviour for 8‐phenyl substituted BODIPYs. The addition of the acceptor nitroso group in compounds 2 (in position β) and 3 (in position α), leads to a different profile. For all the compounds, the nitroso group greatly facilitates the reductions. For compound 3 ( E pIc=−0.238 V), the first to be reduced is the nitroso group, due to the stability of the electrogenerated radical anion, along with non‐bonding interactions with the electronegative boron difluoride. This is different from compound 2 ( E pIc=−0.351 V) with a β‐nitroso group, where the nitroso‐based facilitated reduction occurs in the substituted BODIPY core. Spectroelectrochemistry coupled with analysis through conceptual density functional theory (CDFT) corroborate the voltammetric results and explain the unexpected reactivity differences. Abstract : Positional isomers (α or β) of nitrosyl‐BODIPY exhibit contracting molecular reactivities. Solvent‐influenced, reversible dimer formation of the nitrosyl‐BODIPYs is significant. Spectroelectrochemistry coupled with CDFT analysis explain the unexpected reactivity differences. The nitrosyl group is the first to be reduced in the 5‐nitrosyl‐BODIPY. For the 6‐nitrosyl‐BODIPY, the nitrosyl group strongly facilitates the reduction, which occurs in the BODIPY core. The −NO group on the BODIPY core is the one to be first oxidized, independent on the position in the ring.