2,6-di(pyrimidin-4-yl)pyridine ligands with nitrogen-containing auxiliaries: the formation of functionalized molecular clefts upon metal coordination

Inorg Chem. 2003 Dec 29;42(26):8674-81. doi: 10.1021/ic034823b.

Abstract

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.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cations, Divalent / chemistry
  • Copper / chemistry*
  • Crystallography, X-Ray
  • Guanidine / chemistry
  • Imidazoles / chemistry
  • Kinetics
  • Ligands
  • Organometallic Compounds / chemistry
  • Potentiometry
  • Pyridines / chemical synthesis
  • Pyridines / chemistry*
  • Pyrimidines / chemical synthesis
  • Pyrimidines / chemistry*
  • Quaternary Ammonium Compounds / chemistry
  • Spectrophotometry, Ultraviolet
  • Zinc / chemistry*

Substances

  • Cations, Divalent
  • Imidazoles
  • Ligands
  • Organometallic Compounds
  • Pyridines
  • Pyrimidines
  • Quaternary Ammonium Compounds
  • Copper
  • Zinc
  • Guanidine