2,6-di(pyrimidin-4-yl)pyridine ligands with nitrogen-containing auxiliaries: the formation of functionalized molecular clefts upon metal coordination.
A series of ligands (1-4) based on a 2,6-di(pyrimidin-4-yl)pyridine scaffold have been synthesized, and their abilities to form complexes with Zn(II) and Cu(II) have been determined using UV/vis spectroscopy in buffered aqueous solution (0.01 M N-[2-hydroxyethyl]piperazine-N'-[3-ethanesulfonic acid] (HEPES) at pH = 6.8). The Zn(II) complex of 1 was determined to have a formation constant of 8.4 x 10(3) M(-)(1) while the formation constant of the Cu(II) complex was found to be 1 x 10(6) M(-)(1). The presence of auxiliary amines in 2 increased the stability of the Zn(II) complex relative to that of 1 by a factor of over 40, suggesting possible coordination of the auxiliaries to the Zn(II) center. The guanidinium and 2-amino-4,5-dihydro-imidazolinium groups of 3 and 4 considerably diminished the stability of the Zn(II) and Cu(II) complexes relative to those of 1. X-ray crystal structures of 1-Zn, 3-Zn, 4, and 4-Zn were obtained and are discussed. A significant increase in the stability of 3-Zn, but not in the stability 1-Zn, was observed upon the addition of 1 equiv of sodium phosphate, implicating a stabilizing interaction of the guanidinium groups of 3-Zn and the phosphate anion.
Folmer-Andersen
J Frantz
JF
Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78701, USA.
Aït-Haddou
Hassan
H
Lynch
Vincent M
VM
Anslyn
Eric V
EV
D002413:Cations, Divalent / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D019791:Guanidine / Q000737:chemistry; D007093:Imidazoles / Q000737:chemistry; D007700:Kinetics; D008024:Ligands; D009942:Organometallic Compounds / Q000737:chemistry; D011199:Potentiometry; D011725:Pyridines / Q000138:chemical synthesis / Q000737:chemistry*; D011743:Pyrimidines / Q000138:chemical synthesis / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D015032:Zinc / Q000737:chemistry*
D002413:Cations, Divalent; D007093:Imidazoles; D008024:Ligands; D009942:Organometallic Compounds; D011725:Pyridines; D011743:Pyrimidines; D000644:Quaternary Ammonium Compounds; D003300:Copper; D015032:Zinc; D019791:Guanidine