Molecular enneanuclear Cu phosphates containing planar hexanuclear and trinuclear sub-units: syntheses, structures, and magnetism

• Published in: Dalton transactions : an international journal of inorganic chemistry 2020-02, Vol.49 (8), p.2527-2536
• Main Authors: Santra, Biswajit, Kalita, Pankaj, Chandra, Shubhadeep, Mandal, Debdeep, Kumar, Vierandra, Narayanan, Ramakirushnan Surya, Dey, Atanu, Chrysochos, Nicolas, Huch, Volker, Biswas, Sourav, Ghoshal, Debajyoti, Sañudo, E. Carolina, Sarkar, Biprajit, Schulzke, Carola, Chandrasekhar, Vadapalli, Jana, Anukul
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c9dt04584h

Highly symmetric enneanuclear copper( ii ) phosphates [Cu 9 (Pz) 6 (μ-OH) 3 (μ 3 -OH)(ArOPO 3 ) 4 (DMF) 3 ] (PzH = pyrazole, Ar = 2,6-(CHPh 2 ) 2 -4-R-C 6 H 2 ; R = Me, 2 MeAr ; Et, 2 EtAr ; iPr, 2 iPrAr ; and Ar = 2,6-iPr 2 C 6 H 3 , 2 Dip ) comprising nine copper( ii ) centers and pyrazole, hydroxide and DMF as ancillary ligands were synthesized by a reaction involving the arylphosphate monoester, 1 , copper( i )chloride, pyrazole, and triethylamine in a 4 : 9 : 6 : 14 ratio. All four complexes were characterized by single crystal structural analysis. The complexes contain two distinct structural motifs within the multinuclear copper scaffold: a hexanuclear unit and a trinuclear unit. In the latter, the three Cu( ii ) centres are bridged by a μ 3 -OH. Each pair of Cu( ii ) centers in the trinuclear unit are bridged by a pyrazole ligand. The hexanuclear unit is made up of three dinuclear Cu( ii ) motifs where the two Cu( ii ) centres are bridged by an -OH and a pyrazole ligand. The three dinuclear units are connected to each other by phosphate ligands. The latter also aid the fusion of the trinuclear and the hexanuclear motifs. Magnetic studies reveal a strong antiferromagnetic exchange between the Cu( ii ) centres of the dinuclear units in the hexanuclear part and a strong spin frustration in the trinuclear part leading to a degenerate ground state. Highly symmetric enneanuclear copper( ii ) phosphates comprising of a hexanuclear and a trinuclear motif are described.