Rational design of a photomagnetic chain: bridging single-molecule magnets with a spin-crossover complex.

The spin-crossover complex [Fe(LN5)(CN)2]·H2O (1, LN5 = 2,13-dimethyl-3,6,9-12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene), reported previously by Nelson et al.

Seeking hidden magnetic phenomena by theoretical means in a thiooxoverdazyl adduct.

The oxidation of 1,5-dimethyl-3-(2'-pyridyl)-6-thiooxotetrazane (SvdH(3) py) by benzoquinone leads to a 1:1 adduct of 1,5-dimethyl-3-(2'-pyridyl)-6-thiooxoverdazyl radical (Svdpy) with hydroquinone (hq). The single-crystal X-ray diffraction of this adduct at room temperature (RT) shows that the radicals exhibit a slight curvature that leads to the formation of alternating head-to-tail (antiparallel) stacked 1D chains. Moreover, temperature-dependent X-ray measurements at 100, 200, and 303 K reveal that the lateral slippages between the radicals of the stacks |δ(1) | and |δ(2) | vary from 0.

Nanoscale self-hosting of molecular spin-states in the intermediate phase of a spin-crossover material.

A new spin-crossover (SC) complex [Fe(II)H(2)L(2-Me)][AsF(6)](2) has been synthesized, in which H(2)L(2-Me) denotes the chirogenic hexadentate N(6) Schiff-base ligand bis{[(2-methylimidazol-4-yl)methylidene]-3-aminopropyl}ethylenediamine. This complex has revealed a rich variety of phases during its two-step thermal crossover, as well as photoinduced spin-state switching. A high-symmetry high-spin (HS, S=2) phase, a low-symmetry low-spin (LS, S=0) phase, an intermediate phase characterized by an unprecedented lozenge pattern of 12 predominantly HS molecular crystallographic sites confining 18 predominantly LS molecular crystallographic sites, and a photoinduced low-symmetry HS phase have been accurately evidenced by temperature-dependent magnetic susceptibility, Mössbauer spectroscopy, and crystallographic studies.

Face-sharing heterotrinuclear M(II)-Ln(III)-M(II) (M = Mn, Fe, Co, Zn; Ln = La, Gd, Tb, Dy) complexes: synthesis, structures, and magnetic properties.

Trinuclear linear 3d-4f-3d complexes (3d = Mn(II), Fe(II), Co(II), Zn(II) and 4f = La(III), Gd(III), Tb(III), Dy(III)) were prepared by using a tripodal nonadentate Schiff base ligand, N,N',N''-tris(2-hydroxy-3-methoxybenzilidene)-2-(aminomethyl)-2-methyl-1,3-propanediamine. The structural determinations showed that in these complexes two distorted trigonal prismatic transition metal complexes of identical chirality are assembled through 4f cations. The Mn and Fe entities crystallize in the chiral space group P2(1)2(1)2(1) as pure enantiomers; the cobalt complexes exhibit a less straightforward behavior.

Enhanced ion anisotropy by nonconventional coordination geometry: single-chain magnet behavior for a [{Fe(II)L}2{Nb(IV)(CN)8}] helical chain compound designed with heptacoordinate Fe(II).

Nonconventional heptacoordination in combination with efficient magnetic exchange coupling is shown to yield a 1-D heteronuclear {Fe(II)Nb(IV)} compound with remarkable magnetic features when compared to other Fe(II)-based single chain magnets (SCM). Cyano-bridged heterometallic {3d-4d} and {3d-5d} chains are formed upon assembling Fe(II) bearing a pentadentate macrocycle as the blocking ligand with octacyano metallates, [M(CN)(8)](4-) (M = Nb(IV), Mo(IV), W(IV)). X-ray diffraction (single-crystal and powder) measurements reveal that the [{(H(2)O)Fe(L(1))}{M(CN)(8)}{Fe(L(1))}](infinity) architectures consist of isomorphous 1-D polymeric structures based on the alternation of {Fe(L(1))}(2+) and {M(CN)(8)}(4-) units (L(1) stands for the pentadentate macrocycle).

An unprecedented co-crystal including a cis-high-spin and a trans-low-spin FeII complex molecule.

Two structurally and magnetically nonequivalent isomeric molecules, a cis-high-spin and a trans-low-spin isomer constitute the unit cell of a new iron(II) complex {cis-[FeL(B5)(NCS)(2)].trans-[FeL(B5)(NCS)(2)]}.CH(3)OH, , (L(B5) = N,N'-bis((2-N-methylimidazol-1-yl)methylene))-2,2-dimethylpropane-1,3-diamine); the synthesis, X-ray structure, and magnetic and Mössbauer study of this unique example of co-crystallised geometric, conformational and electronic isomers are reported.

Structural-electronic correlation in the first-order phase transition of [FeH2L2-Me](ClO4)2 (H2L2-Me = bis[((2-methylimidazol-4-yl)methylidene)-3- aminopropyl]ethylenediamine).

The synthesis and detailed study of the new mononuclear spin crossover complex [Fe(II)H2L(2-Me)](ClO4)2 (where H2L(2-Me) = bis[((2-methylimidazol-4-yl)methylidene)-3-aminopropyl]ethylenediamine) are reported. Variable-temperature magnetic susceptibility measurements show the occurrence of a steep spin crossover centered at 171.5 K with a hysteresis loop of ca.

A range of spin-crossover temperature T1/2>300 K results from out-of-sphere anion exchange in a series of ferrous materials based on the 4-(4-imidazolylmethyl)-2-(2-imidazolylmethyl)imidazole (trim) ligand, [Fe(trim)2]X2 (X=F, Cl, Br, I): comparison of experimental results with those derived from density functional theory calculations.

The synthesis and characterization of [FeII(trim)2]Cl2 (2), [FeII(trim)2]Br2MeOH (3), and [FeII(trim)2]I2MeOH (4), including the X-ray crystal structure determinations of 2 (50 and 293 K) and 4 (293 K), have been performed and their properties have been examined. In agreement with the magnetic susceptibility results, the Mössbauer data show the presence of high-spin (HS) to low-spin (LS) crossover with a range of T1/2 larger than 300 K (from approximately 20 K for [FeII(trim)2]F2 (1) to approximately 380 K for 4). All complexes in this series include the same [Fe(trim)2]2+ complex cation: the ligand field comprises a constant contribution from the trim ligands and a variable one originating from the out-of-sphere anions, which is transmitted to the metal center by the connecting imidazole rings and hydrogen bonds.

Complexation to Fe(II), Ni(II), and Zn(II) of multidentate ligands resulting from condensation of 2-pyridinecarboxaldehyde with alpha,omega-triamines: selective imidazolidine/hexahydropyrimidine ring opening revisited.

The condensation reaction between 2-pyridinecarboxaldehyde and diethylenetriamine, 3-[(2-aminoethyl)amino]propylamine, and 3,3'-iminobis(propylamine) in a 2:1 molar ratio yields ligands that may be isolated exclusively in the dissymmetric (cyclic) isomeric forms L(A), L(B)/L(B*), and L(C). The template effect of a metal center (Fe(II), Ni(II), and Zn(II)) results in the ring opening of L(C) including one hexahydropyrimidine ring and one (long) propylene bridge. The resulting symmetric bis-Schiff base isomeric form L(C') is stabilized through pentacoordination, yielding [Fe(II)L(C')(NCS)](NCS) (3), [Ni(II)L(C')(NCS)](NCS) (6), and [Zn(II)L(C')(NCS)](NCS) (9).

High-spin to low-spin relaxation kinetics in the [Fe(TRIM)2]Cl2 complex.

A quasi-quantitative photo-induced low-spin (LS)-->high-spin (HS) conversion of FeII ions has been observed in the [Fe(TRIM)2]Cl2 complex by irradiating the sample with blue light (488 nm) at 10 K. The time dependence of the HS-->LS relaxation has been studied between 10 K and 44 K by means of magnetic susceptibility measurements. These relaxation curves could be satisfactorily fitted by mono-exponential decays including tunnelling effect except for temperatures below 30 K.

A 2D layered spin crossover complex constructed by NH...Cl- hydrogen bonds: [FeIIH3LMe]Cl.I3 (H3LMe = tris[2-(((2-methylimidazoyl-4-yl)methylidene)amino)ethyl]amine.

A 2D layered spin crossover complex, [FeIIH3L(Me)]Cl.I3, has been synthesized from the reaction of FeIIICl3, a tripod ligand (H3LMe = tris[2-(((2-methylimidazoyl-4-yl)methylidene)amino)ethyl]amine), and NaI in methanol. The compound showed an abrupt spin transition between the HS (S = 2) and LS (S = 0) states at T(1/2) = 110 K without hysteresis.

An unprecedented trinuclear structure involving two high-spin and one spin-crossover iron(II) centers.

Anaerobic reaction of ferrous thiocyanate with the deprotonated form of the pentadentate dinucleating Schiff base 1,3-bis[(2-pyridylmethyl)imino]propan-2-ol (LH) yields the novel trinuclear [Fe3L2(NCS)4(H2O)] species 1. LH results from the bis-condensation of 2-acetyl-pyridine with 1,3-diaminopropan-2-ol and includes an N4O donor set. The X-ray crystal structure of 1 [C38H40N12O3S4Fe3, triclinic, space group P-1; a = 10.