43347-AC3
Tailoring of Ligand Functionalization for Improved Lanthanide-Centered Emission in Eu(III) and Tb(III) Complexes
Our group has gained extensive experience in the synthesis of ligands with application as sensitizers of lanthanide ion luminescence and in the characterization of the structural and photophysical properties of the complexes involved.[1-5] We became also interested in studying the effects on the sensitization behavior of derivatizing aromatic carboxylate ligands with nitro functional groups, since our group discovered that lanthanide ion complexes involving nitrobenzoic acid isomers as ligands are luminescent, displaying quantum yields up to 10%.]6, 7] These complexes also proved interesting structurally, as sterically less hindered ligands allowed formation of homobimetallic complexes, while sterically more demanding ligands lead to the isolation of coordination polymers.[8, 9] The presence of the nitro moiety in ligands has kept our attention – while carboxylate moieties are well known to coordinate to lanthanide ions, the similar nitro functional group has received considerably less attention.[10-16] We have thus synthesized new no-carboxylate-bearing ligands with the nitro moiety to study the coordination mode as well as the sensitization ability of these organic molecules.[17] Our group has also successfully developed a new ligand, based on pyridine-bis(oxazoline) (pybox), a tridentate chelating moiety, which is capable of efficiently coordinating lanthanide ions and of very efficiently sensitizing their luminescence. Quantum yields of up to 76% for Eu(III) and 59% for Tb(III) were reported for the sensitization through a pybox derivatized with thiophene at the para position of the pyridine ring.[18] Several more pybox derivatized ligands and lanthanide complexes thereof are currently under investigation as very promising antennas for lanthanide ion luminescence.[19-23] (1) de Bettencourt-Dias, A.; Viswanathan, S.; Ruddy, K. Cryst. Growth Des. 2005, 5, 1477-1484. (2) de Bettencourt-Dias, A. Inorg. Chem. 2005, 44, 2734-2741. (3) de Bettencourt-Dias, A. Curr. Org. Chem. 2007, 11, 1460-1480. (4) de Bettencourt-Dias, A. Dalton Trans. 2007, 2229-2241. (5) de Lill, D. T.; de Bettencourt-Dias, A.; Cahill, C. L. Inorg. Chem. 2007, 46, 3960-3965. (6) de Bettencourt-Dias, A.; Viswanathan, S. Chem. Commun. 2004, 1024-1025. (7) Viswanathan, S.; de Bettencourt-Dias, A. Inorg. Chem. 2006, 45, 10138-10146. (8) Viswanathan, S.; de Bettencourt-Dias, A. Inorg. Chem. Commun. 2006, 9, 444-448. (9) de Bettencourt-Dias, A.; Viswanathan, S. Dalton Trans. 2006, 4093-4103. (10) Bürgstein, M. R.; Roesky, P. W. Angew. Chem. Int. Ed. 2000, 39, 549-551. (11) Bürgstein, M. R.; Gamer, M. T.; Roesky, P. W. Journal of the American Chemical Society 2004, 126, 5213-5218. (12) Yongchi, T.; Guangdi, Y.; Yingqiu, L.; Jiazan, N. Fenzi Kexue Xuebao 1986, 4, 55-62. (13) Ayala, J. D.; Bombieri, G.; Del Pra, A.; Fantoni, A.; Vicentini, G. Inorganica Chimica Acta 1998, 274, 122-125. (14) Ayala, J. D.; Zinner, L. B.; Vicentini, G.; Del Pra, A.; Bombieri, G. Inorganica Chimica Acta 1993, 211, 161-6. (15) Zhang, Y.; Liu, W.; Wang, Y.; Tang, N.; Tan, M.; Yu, K. Journal of Coordination Chemistry 2002, 55, 1293-1299. (16) Fernandes, L. C.; Matos, J. R.; Zinner, L. B.; Vicentini, G.; Zukerman-Schpector, J. Polyhedron 2000, 19, 2313-2318. (17) de Bettencourt-Dias, A.; Viswanathan, S.; Maull, B.; Ayuk, A. in preparation 2008. (18) de Bettencourt-Dias, A.; Viswanathan, S.; Rollett, A. J. Am. Chem. Soc. 2007, 129, 15436-15437. (19) de Bettencourt-Dias, A.; Viswanathan, S.; de Lill, D. T.; Rollett, A. 2008, in preparation. (20) de Bettencourt-Dias, A.; Viswanathan, S.; Ling, G.; Barber, P.; Ayuk, A. 2008, in preparation. (21) de Bettencourt-Dias, A.; Viswanathan, S.; Altun, S. in preparation 2008. (22) de Bettencourt-Dias, A.; de Lill, D. T.; Altun, S. in preparation 2008. (23) de Bettencourt-Dias, A.; de Lill, D. T.; Altun, S. in preparation 2008.
