Ferro- and Antiferromagnetic Interactions in Oxalato-Centered Inverse Hexanuclear and Chain Copper(II) Complexes with Pyrazole Derivatives
oleh: Isabel Castro, M. Luisa Calatayud, Marta Orts-Arroyo, Nicolás Moliner, Nadia Marino, Francesc Lloret, Rafael Ruiz-García, Giovanni De Munno, Miguel Julve
| Format: | Article |
|---|---|
| Diterbitkan: | MDPI AG 2021-05-01 |
Deskripsi
Two novel copper(II) complexes of formulas {[Cu(4-Hmpz)<sub>4</sub>][Cu(4-Hmpz)<sub>2</sub>(µ<sub>3</sub>-ox-<i>κ</i><sup>2</sup><i>O</i><sup>1</sup>,<i>O</i><sup>2</sup>:<i>κO</i><sup>2′</sup>:<i>κO</i><sup>1′</sup>)(ClO<sub>4</sub>)<sub>2</sub>]}<i><sub>n</sub></i> (<b>1</b>) and {[Cu(3,4,5-Htmpz)<sub>4</sub>]<sub>2</sub>[Cu(3,4,5-Htmpz)<sub>2</sub>(µ<sub>3</sub>-ox-<i>κ</i><sup>2</sup><i>O</i><sup>1</sup>,<i>O</i><sup>2</sup>:<i>κO</i><sup>2′</sup>:<i>κO</i><sup>1′</sup>)(H<sub>2</sub>O)(ClO<sub>4</sub>)]<sub>2</sub>[Cu<sub>2</sub>(3,4,5-Htmpz)<sub>4</sub>(µ-ox-<i>κ</i><sup>2</sup><i>O</i><sup>1</sup>,<i>O</i><sup>2</sup>:<i>κ</i><sup>2</sup><i>O</i><sup>2′</sup>,<i>O</i><sup>1′</sup>)]}(ClO<sub>4</sub>)<sub>4</sub>·6H<sub>2</sub>O (<b>2</b>) have been obtained by using 4-methyl-1<i>H</i>-pyrazole (4-Hmpz) and 3,4,5-trimethyl-1<i>H</i>-pyrazole (3,4,5-Htmpz) as terminal ligands and oxalate (ox) as the polyatomic inverse coordination center. The crystal structure of <b>1</b> consists of perchlorate counteranions and cationic copper(II) chains with alternating bis(pyrazole)(µ<sub>3</sub>-<i>κ</i><sup>2</sup><i>O</i><sup>1</sup>,<i>O</i><sup>2</sup>:<i>κO</i><sup>2′</sup>:<i>κO</i><sup>1′</sup>-oxalato)copper(II) and tetrakis(pyrazole)copper(II) fragments. The crystal structure of <b>2</b> is made up of perchlorate counteranions and cationic centrosymmetric hexanuclear complexes where an inner tetrakis(pyrazole)(µ-<i>κ</i><sup>2</sup><i>O</i><sup>1</sup>,<i>O</i><sup>2</sup>:<i>κ</i><sup>2</sup><i>O</i><sup>2′</sup>,<i>O</i><sup>1′</sup>-oxalato)dicopper(II) entity and two outer mononuclear tetrakis(pyrazole)copper(II) units are linked through two mononuclear aquabis(pyrazole)(µ<sub>3</sub>-<i>κ</i><sup>2</sup><i>O</i><sup>1</sup>,<i>O</i><sup>2</sup>:<i>κO</i><sup>2′</sup>:<i>κO</i><sup>1′</sup>-oxalato)copper(II) units. The magnetic properties of <b>1</b> and <b>2</b> were investigated in the temperature range 2.0–300 K. Very weak intrachain antiferromagnetic interactions between the copper(II) ions through the µ<sub>3</sub>-ox-<i>κ</i><sup>2</sup><i>O</i><sup>1</sup>,<i>O</i><sup>2</sup>:<i>κO</i><sup>2′</sup>:<i>κO</i><sup>1′</sup> center occur in <b>1</b> [<i>J</i> = −0.42(1) cm<sup>−1</sup>, the spin Hamiltonian being defined as <b><i>H</i></b> = −<i>J∑<b>S</b></i><sub>1,i</sub> · <b><i>S</i></b><sub>2,i<b>+1</b></sub>], whereas very weak intramolecular ferromagnetic [<i>J</i> = +0.28(2) cm<sup>−1</sup>] and strong antiferromagnetic [<i>J’</i> = −348(2) cm<sup>−1</sup>] couplings coexist in <b>2</b> which are mediated by the µ<sub>3</sub>-ox-<i>κ</i><sup>2</sup><i>O</i><sup>1</sup>,<i>O</i><sup>2</sup>:<i>κO</i><sup>2′</sup>:<i>κO</i><sup>1′</sup> and µ-ox-<i>κ</i><sup>2</sup><i>O</i><sup>1</sup>,<i>O</i><sup>2</sup>:<i>κ</i><sup>2</sup><i>O</i><sup>2′</sup>,<i>O</i><sup>1′</sup> centers, respectively. The variation in the nature and magnitude of the magnetic coupling for this pair of oxalato-centered inverse copper(II) complexes is discussed in the light of their different structural features, and a comparison with related oxalato-centered inverse copper(II)-pyrazole systems from the literature is carried out.