Supramolecular Copper Hydroxide Tennis Balls:  Self-Assembly, Structures, and Magnetic Properties of Octanuclear [Cu₈L₈(OH)₄]⁴⁺Clusters (HL =N-(2-Pyridylmethyl)acetamide)

Abstract

The self-assembly of supramolecular copper "tennis balls" that possess unusual magnetic properties using a small pyridyl amide ligand is described. Copper(II) complexes of N-(2-pyridylmethyl)acetamide (HL) were synthesized in methanol. In the absence of base, the mononuclear complex [Cu(HL)(2)](ClO(4))(2) (1) was prepared. The structure of 1, determined by X-ray crystallography, contains a copper(II) ion surrounded by bidentate HL ligands coordinated via the pyridyl N atom and the carbonyl O atom in a trans, square planar arrangement. Reactions carried out in the presence of triethylamine resulted in cluster complexes [Cu(8)L(8)(OH)(4)](ClO(4))(4) and [Cu(8)L(8)(OH)(4)](CF(3)SO(3))(4) [2(ClO(4))(4) and 2(OTf)(4), respectively]. The cationic portions of 2(ClO(4))(4) and 2(OTf)(4) are isostructural, containing eight copper(II) ions, eight deprotonated ligands (L(-)), and four mu(3)-hydroxide ligands. The top and bottom halves of the cluster are related by a pseudo-S(4) symmetry operation and are held together by bridging L(-) ligands. Solutions of 2(ClO(4))(4) and 2(OTf)(4), which were shown to contain the full [Cu(8)L(8)(OH)(4)](4+) fragment by electrospray mass spectrometry and conductance experiments, are EPR silent. Magnetic susceptibility measurements for 2(ClO(4))(4) as a function of temperature and magnetic field showed the Cu ions all to exhibit magnetic moments in the range expected for the d(9) configuration. At low temperatures, the magnetization was reduced due to predominantly antiferromagnetic interactions between ions. Analysis showed that partially frustrated interactions among the four Cu ions making up each half of the cluster gave good agreement with the data once a large molecular anisotropy was taken into account, with J(c) = 106 cm(-1), D = 27 cm(-1), and g = 2.17.

Self‐assembly process of copper cation and 2,5‐bis(3‐pyridyl)‐1,3,4‐oxadiazole under electrospray ionization conditions

“…18,19 The self-assembly process leading to the formation of the 2:2 complex between 1 and the copper cation in the condensed phase took place in a CH 3 CN/H 2 O (1/1 v/v) solution with Cu(ClO 4 ) 2 (or Cu(NO 3 ) 2 ). 7 The ESI mass spectrum shown in Fig. 1 17 We also found that formation of this complex in the gas phase does not take place when another copper salt ( Fig.…”

Synthesis and Crystal Structure of a Heptanuclear and an Octanuclear Copper(II) Complex Derived from α‐D‐Glucofuranoses

“…By complexation of 2,4,6-triallyloxy-1,3,5-triazin with CuCl or CuCl 2 , Cu 7 and Cu 8 clusters could be isolated. [1] A dimeric tetradecanuclear copper macrocyclic complex with a heptanuclear core structure derived from 2,6-diami-dues of the β-ketoenaminic unit leads to the formation of the octanuclear copper(II) complex Cu(3e).…”

“…[4] Further, linear "tritopic" ligands have been found to assemble copper complexes with higher orders of oligomerisation [5] such as ferromagnetic Cu 8 pinwheel clusters. [6] Copper(II) salts form with N-(2-pyridylmethyl)acetamide, [7] N-propyamine [8] or dipyridyl ketone and 2-hydroxypyridine [9] Cu 8 -clusters. Octanuclear metallamacrocyclic complexes have been synthesised from the pentadentate trianionic Schiff base ligand N,NЈ-(2-hydroxypropane-1,3-diyl)bis(salicylaldimine) [10] or ditopic thiocarbohydrazones.…”

Syntheses and structures of a phenoxo-bridged copper(II) distorted cubane and related complexes with 2-hydroxy-N-(2-pyridylalkyl)benzamide ligands

“…There is only one reported hydroxo-bridged, four-coordinate copper complex with an open cubane-like Cu 4 O 4 framework [3]. Here, we reported the first four-coordinate phenoxo-bridged tetranuclear copper complex with distorted cubane geometry.Recently, our laboratory has focused on the synthesis and characterization of copper clusters using a series of pyridylmethylamide ligands [4][5][6][7][8][9][10]. Pyridyl amide ligands exhibit totally different coordination modes depending on the presence or absence of base used in the synthesis of complexes, since a base will deprotonate the amide group.…”