Inorganic Chemistry, Vol.56, No.21, 13140-13151, 2017
Platinum Complexes of N,N',N '',N'''-Diboronazophenines
Azophenine, (alpha-C6H5NH)(2)(C6H-N=C6H2=N-C6H6), well known to be non-emissive, was rigidified by replacing two amine protons by two difluoroboranes (BF2+) and further functionalized at the pars-positions of the phenyl groups by luminescent trans-ArC C-Pt(PR3)(2)-C C ([Pt]) arms [Ar = C6H4 (R = Et), hexa(n-hexyl)-truxene) (Tru; R = Bu)]. Two effects are reported. First, the linking of these [Pt] arms with the central azophenine (C6H4-N=C6H2(NH)(2)=N-C6H4; Q) generates very low energy charge-transfer (CT) singlet and triplet excited states ((3,1)([Pt]-to-Q)*) with absorption bands extending all the way to 800 nm. Second, the rigidification of azophenine by the incorporation of BF2+ units renders the low-lying CT singlet state clearly emissive at 298 and 77 K in the near-IR region. DFT computations place the triplet emission in the 1200-1400 nm range, but no phosphorescence was detected. The photophysical properties are investigated, and circumstantial evidence for slow triplet energy transfers, (3)Tru* -> Q is provided.