Self-assembly, binding ability and magnetic properties of dicopper() pyrazolenophanes

• Published in: CrystEngComm 2016-01, Vol.18 (3), p.437-449
• Main Authors: Barros, Wdeson P, Luisa Calatayud, M, Lloret, Francesc, Julve, Miguel, Marino, Nadia, De Munno, Giovanni, Stumpf, Humberto O, Ruiz-García, Rafael, Castro, Isabel
• Format: Article
• Language: English
• Subjects: Blocking; Crystal structure; Ligands; Magnetic permeability; Magnetic properties; Pyrazole; Saddles; Self assembly
• ISSN: 1466-8033; 1466-8033
• DOI: 10.1039/c5ce02058a

A novel series of dinuclear copper( ii ) pyrazolenophanes of the formula [Cu 2 (μ-4-Mepz) 2 (μ-ClO 4 )(ClO 4 )(bpm) 2 ] ( 1 ), [Cu 2 (μ-pz) 2 (μ-H 2 O)(ClO 4 )(4,7-Me 2 phen) 2 ]ClO 4 ·H 2 O·CH 3 CN ( 2 ), [Cu 2 (μ-pz) 2 (μ-H 2 O)(ClO 4 ) 3/2 (H 2 O) 1/2 (phen) 2 ] 2 [Cu 2 (μ-pz) 2 (μ-ClO 4 )(ClO 4 ) 2 (phen) 2 ]·8H 2 O ( 3 ), and [Cu 2 (μ-pz) 2 (CH 3 CN) 2 (3,4,7,8-Me 4 phen) 2 ](ClO 4 ) 2 ( 4 ) (Hpz = pyrazole, H-4-Mepz = 4-methylpyrazole, bpm = 2,2'-bipyrimidine, phen = 1,10-phenanthroline, 4,7-Me 2 phen = 4,7-dimethyl-1,10-phenanthroline, and 3,4,7,8-Me 4 phen = 3,4,7,8-tetramethyl-1,10-phenanthroline) have been synthesized and magneto-structurally investigated. The crystal structures of 1-4 contain bis(pyrazolate)(perchlorate)- ( 1 and 3 ), bis(pyrazolate)(aqua)- ( 2 and 3 ), or bis(pyrazolate)-bridged ( 4 ) dicopper( ii ) entities of the metallacyclophane-type with bpm ( 1 ), 4,7-Me 2 phen ( 2 ), phen ( 3 ), and 3,4,7,8-Me 4 phen ( 4 ) as blocking bidentate ligands. All of them exhibit a saddle conformation with an overall not planar but bent, six-membered Cu-(N-N′) 2 -Cu metallacyclic core with relatively short intermetallic distances across the bis(pyrazolate)(perchlorate) [ r = 3.3076(5) ( 1 ) and 3.382(1) Å ( 3 )], bis(pyrazolate)(aqua) [ r = 3.383(1) ( 2 ) and 3.357(1) Å ( 3 )], and bis(pyrazolate) bridges [ r = 3.098(1) Å ( 4 )]. The analyses of the variable-temperature magnetic susceptibility of 1-4 reveal the occurrence of a moderately strong antiferromagnetic coupling across the bis(pyrazolate)(perchlorate) [− J = 228 ( 1 ) and 193 cm −1 ( 3 )], bis(pyrazolate)(aqua) [− J = 189 ( 2 ) and 221 cm −1 ( 3 )], and bis(pyrazolate) bridges [− J = 197 cm −1 ( 4 )] (the spin Hamiltonian being defined as H = − JS 1 · S 2 with S 1 = S 2 = S Cu = ½). The nature of the blocking α-diimine ligand controls of the molecular folding and binding ability of the resulting "butterfly-shaped", antiferromagnetically coupled dicopper( ii ) pyrazolenophanes in the solid state.