Issue 1, 2021

Further synthetic investigation of the general lanthanoid(iii) [Ln(iii)]/copper(ii)/pyridine-2,6-dimethanol/carboxylate reaction system: {Cu II5Ln III4} coordination clusters (Ln = Dy, Tb, Ho) and their yttrium(iii) analogue

Abstract

In addition to previously studied {CuII3Gd6}, {CuII8Gd4}, {CuII15Ln7} and {CuII4Ln8} coordination clusters (Ln = trivalent lanthanide) containing pdm2− or Hpdm ligands (H2pdm = pyridine-2,6-dimethanol) and ancillary carboxylate groups (RCO2), the present work reports the synthesis and study of three new members of a fifth family of such complexes. Compounds [Cu5Ln4O2(OMe)4(NO3)4(O2CCH2But)2(pdm)4(MeOH)2] (Ln = Dy, 1; Ln = Tb, 2; Ln = Ho, 3) were prepared from the reaction of Ln(NO3)3·xH2O (x = 5, 6), CuX2·yH2O (X = ClO4, Cl, NO3; y = 6, 2 and 3, respectively), H2pdm, ButCH2CO2H and Et3N (2 : 2.5 : 2 : 1 : 9) in MeCN/MeOH. Rather surprisingly, the copper(II)/yttrium(III) analogue has a slightly different composition, i.e. [Cu5Y4O2(OMe)4(NO3)2(O2CCH2But)4(pdm)4(MeOH)2] (4). The structures of 1·4MeCN·1.5MeOH and 4·2MeOH were solved by single-crystal X-ray crystallography. The five CuII and four DyIII centres in 1 are held together by two μ5-O2−, four μ-MeO, two syn,syn η11:μ ButCH2CO2, four η2123 pdm2− (each of these groups chelates a CuII atom and simultaneously bridges two DyIII atoms through its two –CH2O arms) and two μ-MeOH ligands. The four terminal nitrato groups each chelate (η11) a DyIII centre. The five CuII atoms are co-planar (by symmetry) forming a bow-tie arrangement; the four outer CuII atoms form a rectangle with edges of 3.061(1) and 6.076(1) Å. The four DyIII centres also form a rectangle that lies above and below the plane of the CuII centres, with edges of 3.739(1) and 5.328(1) Å. The two strictly planar rectangles are almost perpendicular. Two trigonal bipyramidal μ5-O2− groups link the perpendicular Cu5 and Dy4 frameworks together. The molecule 4 has a very similar structure to that of 1, differences being the replacement of the two chelating nitrato groups of 1 by two chelating ButCH2CO2 ligands in 4 and the coordination polyhedra of the LnIII and YIII atoms (Snub diphenoids in 1 and biaugmented trigonal prisms in 4). Dc magnetic susceptibility data (χM) on analytically pure samples of 1–3, collected in the 300–2 K range, indicate that ferromagnetic exchange interactions dominate leading to large spin ground states. The χMT vs. T data for 4 suggest moderately strong antiferromagnetic CuII⋯CuII exchange interactions. Studies of the dynamic magnetic properties of the {Cu5Ln4} clusters show that 1 behaves as a SMM at zero field and 2 is a very weak field-induced SMM, while 3 exhibits only weak tails in the χ′′Mvs. T plots at various ac frequencies at zero dc field.

Graphical abstract: Further synthetic investigation of the general lanthanoid(iii) [Ln(iii)]/copper(ii)/pyridine-2,6-dimethanol/carboxylate reaction system: {CuII5LnIII4} coordination clusters (Ln = Dy, Tb, Ho) and their yttrium(iii) analogue

Supplementary files

Article information

Article type
Paper
Submitted
15 Okt. 2020
Accepted
25 Nov. 2020
First published
25 Nov. 2020
This article is Open Access
Creative Commons BY-NC license

Dalton Trans., 2021,50, 240-251

Further synthetic investigation of the general lanthanoid(III) [Ln(III)]/copper(II)/pyridine-2,6-dimethanol/carboxylate reaction system: {CuII5LnIII4} coordination clusters (Ln = Dy, Tb, Ho) and their yttrium(III) analogue

D. Dermitzaki, C. P. Raptopoulou, V. Psycharis, A. Escuer, S. P. Perlepes, J. Mayans and T. C. Stamatatos, Dalton Trans., 2021, 50, 240 DOI: 10.1039/D0DT03582C

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