TY - JOUR
T1 - Controlled Formation of Heteroleptic [Pd2(La)2(Lb)2]4+ Cages
AU - Preston, Dan
AU - Barnsley, Jonathan E.
AU - Gordon, Keith C.
AU - Crowley, James D.
N1 - Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/8/24
Y1 - 2016/8/24
N2 - Metallosupramolecular architectures are beginning to be exploited for a range of applications including drug delivery, catalysis, molecular recognition, and sensing. For the most part these achievements have been made with high-symmetry metallosupramolecular architectures composed of just one type of ligand and metal ion. Recently, considerable efforts have been made to generate metallosupramolecular architectures that are made up of multiple different ligands and/or metals ions in order to obtain more complex systems with new properties. Herein we show that the addition of an electron-rich 2-amino-substituted tripyridyl ligand, 2,6-bis(pyridin-3-ylethynyl)pyridine (2A-tripy), to a solution of the [Pd2(tripy)4]4+ cage resulted in the clean generation of a heteroleptic [Pd2(tripy)2(2A-tripy)2]4+ architecture. The formation of the mixed-ligand cage [Pd2(tripy)2(2A-tripy)2]4+ was confirmed using 1H NMR spectroscopy, diffusion-ordered spectroscopy, and rotating-frame nuclear Overhauser effect spectroscopy and high-resolution electrospray ionization mass spectrometry. Density functional theory calculations suggested the cis isomer was more stable that the trans isomer. Additionally, the calculations indicated that the heteroleptic palladium(II) cages are kinetically metastable intermediates rather than the thermodynamic product of the reaction. Competition experiments supported that finding and showed the cages are long-lived in solution at room temperature. Finally, it was shown that the addition of 2A-tripy to a range of preformed [Pd2(Ltripy)4]4+ cages cleanly generated the mixed-ligand systems. Three other systems displaying different exo and endo functionalities within the cage assembly were generated, suggesting that this method could be applied to synthesize a range of highly functionalized heteroleptic cis-[Pd2(La)2(Lb)2]4+ cages.
AB - Metallosupramolecular architectures are beginning to be exploited for a range of applications including drug delivery, catalysis, molecular recognition, and sensing. For the most part these achievements have been made with high-symmetry metallosupramolecular architectures composed of just one type of ligand and metal ion. Recently, considerable efforts have been made to generate metallosupramolecular architectures that are made up of multiple different ligands and/or metals ions in order to obtain more complex systems with new properties. Herein we show that the addition of an electron-rich 2-amino-substituted tripyridyl ligand, 2,6-bis(pyridin-3-ylethynyl)pyridine (2A-tripy), to a solution of the [Pd2(tripy)4]4+ cage resulted in the clean generation of a heteroleptic [Pd2(tripy)2(2A-tripy)2]4+ architecture. The formation of the mixed-ligand cage [Pd2(tripy)2(2A-tripy)2]4+ was confirmed using 1H NMR spectroscopy, diffusion-ordered spectroscopy, and rotating-frame nuclear Overhauser effect spectroscopy and high-resolution electrospray ionization mass spectrometry. Density functional theory calculations suggested the cis isomer was more stable that the trans isomer. Additionally, the calculations indicated that the heteroleptic palladium(II) cages are kinetically metastable intermediates rather than the thermodynamic product of the reaction. Competition experiments supported that finding and showed the cages are long-lived in solution at room temperature. Finally, it was shown that the addition of 2A-tripy to a range of preformed [Pd2(Ltripy)4]4+ cages cleanly generated the mixed-ligand systems. Three other systems displaying different exo and endo functionalities within the cage assembly were generated, suggesting that this method could be applied to synthesize a range of highly functionalized heteroleptic cis-[Pd2(La)2(Lb)2]4+ cages.
UR - http://www.scopus.com/inward/record.url?scp=84983652265&partnerID=8YFLogxK
U2 - 10.1021/jacs.6b05629
DO - 10.1021/jacs.6b05629
M3 - Article
SN - 0002-7863
VL - 138
SP - 10578
EP - 10585
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 33
ER -