Charge-Transfer Transitions Govern the Reactivity and Photophysics of Vicinally Diphosphanyl-Substituted Diborapentacenes.

2,3-Difluoro-5,14-dihydro-5,14-diborapentacene (DBP) was endowed with two vicinal Ph 2 P groups by an S N Ar reaction at both CF sites using Ph 2 PSiMe 3 . Computations reveal the ambipolar product P to undergo P-to-B charge transfer under ambient light irradiation. Consequently, P is prone to photooxidation by air, yielding the Ph 2 P(O) species PO. With S 8 or [Me 3 O][BF 4 ], P furnishes the Ph 2 P(S) or Ph 2 P(Me) + derivatives PS or [PMe][BF 4 ] 2 . Along the series P, PO, PS, and [PMe][BF 4 ] 2 , the redox potentials shift anodically from E 1/2 =-1.89 V to -1.02 V (CH 2 Cl 2 ). Thus, derivatization of the Ph 2 P group allows late-stage modulation of the LUMO-energy level of the DBP. Derivatization also influences the emission properties of the compounds, as PO shows green (521 nm) and [PMe][BF 4 ] 2 red (622 nm) fluorescence in C 6 H 6 , while P and PS are dark. With CuBr and AgBr, P forms dimeric [M(μ-Br)] 2 complexes [PCu] 2 and [PAg] 2 , which show pronounced metal-to-ligand charge transfer (MLCT), making P a promising ligand for photocatalysts.