PYRIDYL-FUNCTIONALIZED, BIPYRIDYL-FUNCTIONALIZED, AND TERPYRIDYL-FUNCTIONALIZED AZAMACROCYCLES

A series of azamacrocycles which have been N-functionalised with pende nt pyridylmethyl-(pyCH(2)-), bipyridylmethyl-(bipyCH(2)-) and terpyrid ylmethyl- (terpyCH(2)-) arms have been synthesised and characterised, and some of their coordination chemistry with transition metal ions is reported. By attaching the pendent-arms at the 5- rather than the 6-p osition of the py, bipy and terpy, new ligands are generated which can be used to form polynuclear metal complexes in a controlled and syste matic fashion. Fluorescent pH and transition metal ion sensors have be en developed by reacting the azamacrocyclic N-pendent bipyCH(2) arm(s) with cis-[Ru(bipy)(2)Cl-2] to give macrocycles with up to four attach ed [Ru(bipy)(3)](2+) groups. That based on 1,4,7-triazacyclononane (9N 3), with three attached [Ru(bipy)(3)](2+) groups, has a first photo ex cited state pK(a) of 7.1, and is a useful fluorescent sensor for physi ological pH at below micromolar concentrations. The analogous derivati ve of cyclam (1,4,8,11-tetraazacyclotetradecane) carrying four [Ru(bip y)(3)](2+) groups has a first photo excited state pK(a) of 5.7, allowi ng kinetic and thermodynamic fluorescence studies of metal ion uptake by an azamacrocycle at neutral pH without complications from protonate d species. A pre-organised hexadentate tris(2,2'-bipyridyl) chelating ligand, 1,4,7-tris(2',2 ''-bipyridyl-5'-ylmethyl)-1,4,7-triazacyclonon ane (L) has been developed, and crystal structures of mononuclear comp lexes [M(LH)](3+) (M = Ru, Cu) are reported. In [M(LH)](3+) the azamac rocyclic N-atoms are noncoordinating to M, but have a very high affini ty for a single proton trapped in the macrocyclic cavity, An analogous and potentially nonadentate ligand has been developed based on 9N3 wi th three N-pendent terpyCH(2)-arms.