The coordination number-photophysical properties relationship of trianthrylphosphorus compounds: doubly locked fluorescence of anthryl groups

A series of tri(9-anthryl)phosphorus compounds including tri(9-anthryl)methylphosphonium iodide (2b), tri(9-anthryl)phophine oxide (2c), and tri(9-anthryl)difluorophosphorane (2d) have been newly synthesized from the already reported tri(9-anthryl)phosphine (2a) and their photophysical properties including UV-vis absorption and fluorescence spectra have been determined in order to elucidate their coordination number-properties relationships. It has been found that their characteristic fluorescence properties are highly dependent on the coordination number of the central phosphorus atom. Thus, while the tri-coordinate phosphine 2a and the tetra-coordinate phosphonium salt 2b and phosphine oxide 2c show no and weak (Phi(f) < 0.01) fluorescence, respectively, the penta-coordinate phosphorane 2d exhibits intense fluorescence (Phi(f) = 0.28) which is comparable to that of the parent anthracene. (C) 2002 Elsevier Science B.V. All rights reserved.