High Stokes shift long-wavelength energy gap regulated fluorescence in the series of nitro/dimethylamino-substituted ortho-analogs of POPOP

A series of novel nitro-substituted ortho-analogs of POPOP was synthesized. Like the most of the other known compounds of this class, the synthesized molecules demonstrate high Stokes shift fluorescence emission owing to the planarization of their molecules at electronic excitation. Significant fluorescence quenching in polar solvents was described as the “energy gap law” action rather than the specific effect of the dialkylamino group excited state twisting.

peri-Interactions in Naphthalenes, 6 [1]. On Hypercoordination of Phosphorus in 8-Dialkylamino-naphth-1-yl Phosphonium Salts

Under favourable conditions, the phosphorus centres in tetraorganophosphonium cations are sufficiently electrophilic to become hypercoordinate by reaction with strong nucleophiles. However, as a peri substituent at the naphthalene system, such a centre proved to be unable to induce the nitrogen of a peri-bound dialkylamino group to bond formation. The distortion of the naphthalene skeleton revealed by X-ray structure determination of four 8-dialkylaminonaphth- 1-yl phosphonium salts does not exhibit the criteria of N-P bond formation but rather those of intersubstituent repulsion.