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7617856 
Journal Article 
FROM P-DIMETHOXYBENZENE TOWARD CROWN BENZENOPHANES - 1,3,10,14-TETRAOXA[3.5]PARACYCLOPHANE 
Hopf, H; Utermohlen, R; Jones, PG; Desvergne, JP; Bouaslaurent, H; , 
1992 
Yes 
Journal of Organic Chemistry
ISSN: 0022-3263
EISSN: 1520-6904 
AMER CHEMICAL SOC 
WASHINGTON 
5509-5517 
WOS:A1992JQ22700038 
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.