In situ hydrolysis of a carbophosphazene ligand leads to one-dimensional lanthanide coordination polymers. Synthesis, structure and dynamic magnetic studies.

An in situ hydrolysis of the P-Cl bonds of the carbophosphazene [{NC(NMe2)}2{NPCl2}] (LPCl2) in the presence of hydrated lanthanide(III) nitrates in a dichloromethane and methanol (2 : 1) solvent mixture afforded a series of novel 1D coordination polymers: [{Ln(LHPO2)3(NO3)2(CH3OH)(H2O)} (Cl)]n {where Ln(III) = Gd (1), Tb (2), Dy (3), or Er (4) and LHPO2 is the hydrolyzed carbophosphazene (LPCl2) ligand}. X-ray crystallographic analysis revealed that complexes 1-4 are isostructural and crystallized in the monoclinic crystal system having P21/c space group. The coordination polymers are formed because of the involvement of the geminal P(O)(OH) moieties of the carbophosphazene ligand. Each lanthanide(III) ion is 9-coordinate (9O) in a distorted muffin geometry. Magnetic measurements revealed that both DyIII and ErIII analogues exhibit field-induced single-molecule magnet (SMM) behavior at 0.8 kOe and 2.2 k Oe, respectively. At such dc fields, the dynamic magnetic susceptibility displays complex behavior with a triple magnetic relaxation contribution for 3, while two contributions were identified for 4. The observed static and dynamic magnetic behavior for complexes 1-4 were further rationalized with the aid of BS-DFT and CASSCF/SO-RASSI/SINGLE_ANISO calculations.

A single-ion magnet building block strategy toward Dy2 single-molecule magnets with enhanced magnetic performance.

A molecular dysprosium(III) complex [Dy(DClQ)3(H2O)2] (1) was used as a building unit for the construction of lanthanide SMMs, leading to the isolation of two dinuclear Dy(III) complexes, namely [Dy2(DClQ)6(MeOH)2] (2) and [Dy2(DClQ)6(bpmo)2]·6MeCN (3) (DClQ = 5,7-dichloro-8-hydroxyquinoline, bpmo = 4,4'-dipyridine-oxide). Structural analyses revealed the same N3O5 coordination environment of the Dy(III) centers with a distorted biaugmented trigonal prism (C2V symmetry) and triangular dodecahedron (D2d symmetry) for 2 and 3, respectively. Magnetic studies revealed the presence of ferromagnetic and weak antiferromagnetic exchange interactions between the Dy3+ centers in 2 and 3, respectively. Interestingly, slow relaxation of magnetization at zero fields was evidenced with an Ueff of 51.4 K and 159.0 K for complexes 2 and 3, respectively. The detailed analysis of relaxation dynamics discloses that the Orbach process is dominant for 2 whereas Raman and QTM play an important role in 3. Theoretical calculations were carried out to provide insight into the magnetic exchange interactions and relaxation dynamics for the complexes. Due to a single-ion magnet (SIM) of 1, the foregoing results demonstrate a SIM modular synthetic route for the preparation of dinuclear lanthanide SMMs.