MOLECULAR ASSOCIATION MEDIATED BY NITROGEN-CHLORINE DONOR-ACCEPTOR INTERACTIONS

3,5-Bis(2-pyridylethynyl)-4-chloronitrobenzene (5) and 3,5-bis[[3-(4-( tert-butylbenzyl)oxy)-2-pyridyl]- ethynyl]-4-chloronitrobenzene (13) w ere synthesized as potential tridentate ligands, via nitrogen-chlorine donor-acceptor interactions, of 2,6-dichloropyridine and related comp ounds. Compound 5 was also synthesized in N-15-labeled form, and its a ssociation with 2,6-dichloropyridine, 2,6-dibromopyridine, 2,4,6-trich loropyrimidine, and 1,3-dichlorobenzene was examined by means of N-15 NMR titration experiments. The first three compounds were weakly assoc iated with 5 (K-assoc = 0.2-0.3 M(-1)) in toluene solution and induced significant upfield shifts in its N-15 NMR resonances, but 1,3-dichlo robenzene, which cannot fit satisfactorily into the proposed ''cleft'' of compound 5, had little effect. The X-ray structure of 5 and the pr oposed structures of its complexes are discussed.