From para-dimethoxybenzene toward crown benzenophanes: 1,3,10,14-tetraoxa[3.5]paracyclophane
摘要:
The title compound tetraoxa[3.5]paracyclophane (6) has been prepared and studied in order to investigate the evolution of spectroscopic properties in going from the monomer unit p-dimethoxybenzene (9) via the noncyclic bichromophoric reference compound 3b to 6. The X-ray structural analysis of 6 shows that the distance between the two aromatic carbon atoms linked to the smaller bridge is shorter than the van der Waals distance. The resulting electronic interaction is reflected by the perturbation of the UV spectrum of 6 (in particular by a distinct hypochromic effect) and in its charge-transfer complexes with TCNE and TCNQ, as compared to 9 and 3b. The fluorescence quantum yields show significant quenching as compared to 9. This process is related to the formation of a new, structureless red-shifted band with a maximum at 26 670 cm-1, comparable to that of the excimer of 9. From a Stern-Volmer plot the self-quenching rate constant of the latter, k(q) almost-equal-to 1.2 x 10(9) mol-1 s-1 is derived.
From para-dimethoxybenzene toward crown benzenophanes: 1,3,10,14-tetraoxa[3.5]paracyclophane
作者:Henning Hopf、Ralf Utermoehlen、Peter G. Jones、Jean Pierre Desvergne、Henri Bouas-Laurent
DOI:10.1021/jo00046a038
日期:1992.9
The title compound tetraoxa[3.5]paracyclophane (6) has been prepared and studied in order to investigate the evolution of spectroscopic properties in going from the monomer unit p-dimethoxybenzene (9) via the noncyclic bichromophoric reference compound 3b to 6. The X-ray structural analysis of 6 shows that the distance between the two aromatic carbon atoms linked to the smaller bridge is shorter than the van der Waals distance. The resulting electronic interaction is reflected by the perturbation of the UV spectrum of 6 (in particular by a distinct hypochromic effect) and in its charge-transfer complexes with TCNE and TCNQ, as compared to 9 and 3b. The fluorescence quantum yields show significant quenching as compared to 9. This process is related to the formation of a new, structureless red-shifted band with a maximum at 26 670 cm-1, comparable to that of the excimer of 9. From a Stern-Volmer plot the self-quenching rate constant of the latter, k(q) almost-equal-to 1.2 x 10(9) mol-1 s-1 is derived.