Four heterometallic dinuclear CuIILnIII (Ln = Tb and Dy) complexes derived from two different N2O3 donor unsymmetrical Schiff base ligands exhibit SMM behaviour.
Five new heterometallic Cu(II)-Mn(II) discrete trinuclear complexes, [(CuL)2Mn(CH3COO)2] (1), [(CuL)2Mn(NO3)2] (2), [(CuL)2Mn(C6H5COO)(H2O)]Cl (3), [(CuL)2Mn((p-OH)C6H5COO)(H2O)]ClO4 (4) and [(CuL)2Mn(HCOO)(H2O)]ClO4 (5) have been synthesized using a metalloligand, CuL derived from an N2O2 donor...
The
reaction of the mononuclear Ni(II) building block [NiL] of
an asymmetrically dicondensed N2O3 donor Schiff
base ligand, N-salicylidene-N′-3-methoxysalicylidene-1,3-propanediamine
(H2L), with LnCl3·6H2O (Ln =
Gd, Tb, Dy) in a 2:1 molar ratio leads to the formation of three hexanuclear
carbonato-bridged Ni4Ln2 complexes formulated
as [Ni4Ln2(CO3)2Cl2(L)2(L′)2(CH3CN)2]·4CH3CN·2H2O (Ln = Tb (2), Dy (3)), where H2L′ = N,N′-bis(salicylidene)-1,3-propanediamine. In complex 1, the unsymmetrical nature of the Schiff base remains intact;
however, in 2 and 3, between the two metalloligands
coordinated to each Ln, one is the precursor [NiL] of the unsymmetrical
ligand whereas the other [NiL′] of the symmetrical ligand,
formed by an in situ aldehyde-exchange reaction during
complex formation with Ln salts. The Ln(III) centers are octacoordinated
with a biaugmented-trigonal-prismatic geometry in all three complexes.
In complex 1, half of the Ni(II) centers possess a distorted
octahedral geometry while the other half has a square-pyramidal geometry;
all of the Ni(II) centers in complexes 2 and 3 have a distorted-octahedral geometry. A magnetic study clarifies
that the Ni–Ln magnetic exchange couplings are ferromagnetic.
Though the complexes consist of a hexanuclear [Ln2Ni4] system, the magnetic properties have been analyzed on a
trinuclear Ni–Ln–Ni basis. The exchange parameter 2J
Gd–Ni/k
B in 1 was estimated to be +0.61 to +0.84 K across the double-oxide
bridges. Complexes 2 and 3 exhibited an
indication of single-molecule magnets in an ac susceptibility study.
Four new heterometallic Cu(II)−U(VI) species, [{(CuL 1 )-(CH 3 CN)}UO 2 (NO 3 ) 2 ] (1), [{(CuL 2 )(CH 3 CN)}UO 2 (NO 3 ) 2 ] (2), [{(CuL 3 )(H 2 O)}UO 2 (NO 3 ) 2 ] (3), and [UO 2 (NO 3 ) 2 (H 2 O) 2 ]•2[CuL 4 ]•H 2 O (4), were synthesized using four different metalloligands ([CuL 1 ], [CuL 2 ], [CuL 3 ], and [CuL 4 ], respectively) derived from four unsymmetrically dicondensed N,O-donor Schiff bases. Single-crystal structural analyses revealed that complexes 1, 2, and 3 have a discrete dinuclear [Cu−UO 2 ] core in which one metalloligand, [CuL], is connected to the uranyl moiety via a double phenoxido bridge. Two chelating nitrate ions complete the octacoordination around uranium. Species 4 is a cocrystal, where a uranyl nitrate dihydrate is sandwiched between two metalloligands [CuL 4 ] by the formation of strong hydrogen bonds between the H atoms of the coordinated water molecules to U(VI) and the O atoms of [CuL 4 ]. Spectrophotometric titrations of these four metalloligands with uranyl nitrate dihydrate in acetonitrile showed a well-anchored isosbestic point between 300 and 500 nm in all cases, conforming with the coordination of [CuL 1 ], [CuL 2 ], [CuL 3 ], and the H-bonding interaction of [CuL 4 ] with UO 2 (NO 3 ) 2 . This behavior of [CuL 4 ] was utilized to selectively bind metal ions (e.g., Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , and La 3+ ) in the presence of UO 2 (NO 3 ) 2 •2H 2 O in acetonitrile. The formation of these Cu(II)−U(VI) species in solution was also evaluated by steady-state fluorescence quenching experiments. The difference in the coordination behavior of these metalloligands toward [UO 2 (NO 3 ) 2 (H 2 O) 2 ] was studied by density functional theory calculations. The lower flexibility of the ethylenediamine ring and a large negative binding energy obtained from the evaluation of H bonds and supramolecular interactions between [CuL 4 ] and [UO 2 (NO 3 ) 2 (H 2 O) 2 ] corroborate the formation of cocrystal 4. A very good linear correlation (r 2 = 0.9949) was observed between the experimental UO stretching frequencies and the strength of the equatorial bonds that connect the U atom to the metalloligand.
Three field induced SMMs built from quasi isotropic cations like CuII and MnII have been characterized, showing that relatively large clusters with quasi negligible D and different ground spin state,...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.