No abstract

A series of thirteen complexes which may be formally considered as assembled from Cu(bpy)2(NO3)2 and Ln(NO3)3 (Ln=La−Yb excluding Pm, bpy=2,2’‐bipyridine) have been characterized. The crystals may be grouped into four classes: A, [Cu2(bpy)4(μ‐NO3)][Ln(NO3)6] (Ln=La−Nd); B, [Cu(bpy)2(NO3)]2[Ln(NO3)4(OH2)2](NO3) (Ln=Sm−Dy); C, [Cu(bpy)2(NO3)]2[Ln(NO3)5] (Ln=Ho−Tm); D, [Cu(bpy)2(NO3)]2 [Ln(NO3)3(OH2)3](NO3)2⋅2H2O (Ln=Yb). The coordination numbers of the nitrato or aquonitrato lanthanide anions range from 9 to 12. The dinuclear cation in Class A having a linear monoatomic nitrate bridge is new and is seen to produce weak antiferromagnetic coupling in these compounds. The other classes contain distortion isomers of [Cu(bpy)2NO3]+. The structural trends are analysed in terms of lanthanide contraction and non‐covalent interactions in the crystals. EPR and electronic spectral characteristics are discussed for the four classes of compounds.

No abstract

A series of thirty six complexes obtained from acetonitrile solutions of Cu(NO 3 ) 2 , Ln(NO 3 ) 3 and 2,2-biyridine or 5,5-dimethyl-2,2-bipyridine (Ln = La-Yb excluding Pm) have been characterized. The crystals may be grouped into six types: Type-I, [Cu(bpy) 3 ][La(NO 3 ) 5 (OH 2 )]; Type-II, [Cu(bpy) 3 ][Ln-(NO 3 ) 5 (OH 2 )] ⋅ 2CH 3 CN (Ln = Ce, Pr); Type-IIa, [Cu(5,5dmbpy) 3 ][Ln(NO 3 ) 5 (OH 2 )] ⋅ 2CH 3 CN (Ln = La, Ce); Type-III, [Cu-(bpy) 3 ][Ln(NO 3 ) 5 ] (Ln = Nd, Sm-Lu); Type-IIIa [Cu(5,5dmbpy) 3 ][Ln(NO 3 ) 5 ] (Ln = Pr, Nd, Sm-Lu); Type-IV, [Cu(5,5dmbpy) 2 (NO 3 )] 2 [Ln(NO 3 ) 5 (OH 2 )]⋅CH 3 CN [Ln = La-Nd, Sm-Tb). The coordination numbers of the nitrato and aquonitrato lanthanide anions are 10 and 11, respectively. The tris-chelates in Types I, II and IIIa undergo static Jahn-Teller distortion while Types IIa and III support fluxional tris-chelate ions. Type-IV contains distortion isomers of [Cu(5,5-dmbpy) 2 NO 3 ] + . The structural trends are analysed in terms of lanthanide contraction and non-covalent interactions in the crystals. EPR and electronic spectral characteristics are discussed for the six types of compounds.

Two new triply bridged Cu(II) compounds [Cu3(bpy)2(μ‐ClCH2COO)6] (1) and [Cu2(bpy)2(μ‐OH)(μ‐OH2)(μ‐ClCH2COO)](ClO4)2 (2) (where, bpy=2,2’‐bipyridine) have been synthesized and their magnetic properties have been measured and correlated with structure. Compound 1 is a novel centrosymmetric tricopper compound with only carboxylate bridges. The terminal Cu2+ ions have [5 + 1] coordination while the central ion has [4 + 2] coordination. The three centres are antiferromagnetically coupled, the exchange parameters for the neighbouring and distant pairs of Cu(II) atoms being 2 J=–28.6 cm–1 and 2 J'=–1.0 cm–1, respectively. In compound 2 three types bridging modes are observed, viz., hydroxo, aquo and carboxylato. The two Cu(II) centers are ferromagnetically coupled (2 J=73.8 cm–1) as previously observed for several di‐copper complexes with the same bridges. DFT calculations are in reasonable agreement with the magnetic exchange parameters for both dinuclear and trinuclear compounds.