title: Nickel(II)-dipeptidoamine-based tetrameric complex: structural study in solution and in solid state.
abstract: The coordination structure of M(4)L(4)H(-8) macromolecules (M = Ni(II), Cu(II), Pd(II)) containing small peptidic ligands (L = Xaa-His or Xaa-His-Yaa) has been predicted primarily on the basis of spectroscopic and potentiometric data in the literature. In this work, the neutral tetranuclear nickel(II) complex 1 formed with four double-deprotonated ligands (L = α-methyl-alanyl-histamine) was prepared, and its crystal structure was determined (C(36)H(56)N(16)Ni(4)O(4)·4.5CH(3)OH·1.5H(2)O: a = 11.2645(4) A, b = 23.5003(8) A, c = 20.9007(7) A, β = 102.321(1)°, monoclinic, P2(1)/c, Z = 4). In complex 1, the metal ions have a square planar geometry with 4N donor set consisting of the N-terminal amino nitrogen, the deprotonated amide nitrogen, the imidazole N(3) atom, and the deprotonated imidazole N(1) atom of the adjacent ligand. The latter nitrogen atom provides the connection of the four NiLH(-2) units forming a C(1) symmetrical saddle-like shape. The complexation of L with Ni(II) ion has been studied by a potentiometric method combined with UV-visible spectrophotometric titration. At pH 8.0, the predominant species is M(4)L(4)H(-8) with pK(4)(oligomerization) = 5.73. The tetranuclear structure of complex 1 was also studied in solution by (1)H and (13)C NMR spectroscopy suggesting a structure of symmetry S(4). DFT calculations on optimized structure in symmetry C(1) and S(4) have been performed to explain the observed differences in solution and in solid state. The nuclearity was also confirmed in solution by ESI-HRMS analysis.
authors: Laboratoire SRSMC (UMR 7565 CNRS-Université Henri Poincaré Nancy 1), BP 70239, F-54506 Vandoeuvre-lès-Nancy Cedex, France. katalin.selmeczi@srsmc.uhp-nancy.fr
authors: Katalin
authors: K
authors: Selmeczi
authors: Patrick
authors: P
authors: Gizzi
authors: Delphine
authors: D
authors: Champmartin
authors: Patrice
authors: P
authors: Rubini
authors: Emmanuel
authors: E
authors: Aubert
authors: Slimane
authors: S
authors: Dahaoui
authors: Bernard
authors: B
authors: Henry
mesh_terms: D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D009532:Nickel / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D011522:Protons; D012996:Solutions; D013057:Spectrum Analysis
chemical_list: D008024:Ligands; D009942:Organometallic Compounds; D010455:Peptides; D011522:Protons; D012996:Solutions; D009532:Nickel