μ‐η¹:η¹‐N,N'‐Imidazolidine‐Bridged Dicopper(II/III) Complexes of a New Dinucleating μ‐Bis(tetradentate) Schiff Base Ligand: Synthesis, Structural Characterization, ¹H NMR Spectroscopy, and Magnetic Coupling

Abstract

The copper coordination chemistry of a new imidazolidine‐based doubly bridging μ‐bis(tetradentate) ligand, H3mhbai is studied. A new family of pentacoordinate dinuclear complexes of formula [CuII2(‐mhbai)(‐X)]·2 H2O (1–4) [X = OAc, NO3, Cl, S2COMe], where H3mhbai stands for 2‐(2‐hydroxyphenyl)‐1,3‐bis[4‐(2‐hydroxyphenyl)‐4‐methyl‐3‐aza‐but‐3‐enyl]‐2‐methyl‐1,3‐imidazolidine, were synthesized from the ligand, H3mhbai in air. The complex 1 was structurally characterized by X‐ray crystallography. The μ‐η1:η1‐N,N'‐imidazolidine bridging mode between two copper(II) ions has been identified in this complex along with a nonhelical binding mode of the μ‐bis(tetradentate) ligand. Variable temperature (2–300 K) magnetic susceptibility data of 1 show the presence of a weak antiferromagnetic exchange interaction between the two triply bridged magnetically isolated copper(II) (S = 1/2) ions. The χmT values start to drop at temperature below 50 K, to reach a value of 0.55 cm3 K mol–1 at 2 K for a coupling constant value of J = –2.2 cm–1. The 1H NMR spectrum of the weakly coupled complex 1 shows a total of seventeen hyperfine shifted peaks, as expected from the idealized Cs symmetry of the compound, spread over a very large window of chemical shift, spanning about 130 ppm. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

[CuII4] Clusters From the Self‐Assembly of Two Imidazolidinyl 2‐Phenolate‐Bridged [CuII2] Units: The Role of the Chloride Bridge

“…The nature of the final reaction product is greatly influenced by the ligand, solvent system and sequence of addition of the reactants. For example, under similar reaction conditions H 3 L and a substituted analogue of H 3 L (H 3 mhbai in ref 1415 react differently with NaN 3 to give the cation‐ and anion‐centred tetranuclear copper complexes [NaCu 4 L 2 (N 3 ) 2 ]ClO 4 · H 2 O11 and [Cu 4 L 2 (N 3 )]Cl · 16H 2 O,15 respectively.…”

[(Tmp)Co2L] Complexes through Preassembly on 2,6‐Diformyl‐ and 2,6‐Bis(benzylimino)‐4‐methylphenolate Templates

“…[7] We and others have been exploring the dinucleating properties of the ligand H 3 L (Scheme 1) {2-(2Ј-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine} [8] and its close derivative H 3 LЈ {2-(2Ј-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-4-methyl-3-aza-on these templates before coordination with L 3- but-3-enyl]-2-methyl-1,3-imidazolidine} [9] for various reasons, including their importance in coordination chemistry, molecular magnetism, and catalysis. [9][10][11][12][13][14][15][16] Scheme 1. During the course of these investigations, we have observed that in certain conditions, complexation reactions with Mn III , Fe III , Co III , or Cu II led to the hydrolysis of the imidazolidine ring [17,18] and even the destruction of one of the imine linkages of the hexadentate proligand. [19] We have also investigated the hydrolysis of H 3 L as triggered by Co III and isolated the mononuclear complex resulting from the hydrolyzed ligand.…”

Trapping of a Methanoato Bridge in µ‐1,1,3,3 Mode for [Cu4] Aggregate Formation: Synthesis, Steric Control on Nuclearity, Antimicrobial Activity, and DNA‐Interaction Properties

“…The most studied examples of imidazolidine‐based dinucleating ligands are 2‐(2′‐hydroxyphenyl)‐1,3‐bis[4‐(2‐hydroxyphenyl)‐3‐azabut‐3‐enyl]‐1,3‐imidazolidine,[9a], 2‐(2′‐hydroxyphenyl)‐1,3‐bis[4‐methyl‐4‐(2‐hydroxyphenyl)‐3‐azabut‐3‐enyl]‐1,3‐imidazolidine, and 2‐methyl‐2‐(2′‐hydroxyphenyl)‐1,3‐bis[4‐methyl‐4‐(2‐hydroxyphenyl)‐3‐azabut‐3enyl]‐1,3‐imidazolidine. [9b], …”