Decorating BODIPY with Electron-Withdrawing NO Group: Spectroelectrochemical Consequences and Computational Investigation

4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene (BODIPY) and derivatives are an outstanding class of fluorescent dyes, We, herein, report the effect of 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 -Bu 4 NPF 6 (0.1 M), 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, differently 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.