Crystal structure of bis-{5-(4-chloro-phen-yl)-3-[6-(1-pyrazol-1-yl)pyridin-2-yl]-1-1,2,4-triazol-1-ido}nickel(II) methanol disolvate.

The unit cell of the title compound, [Ni(CHClN)]·2CHOH, consists of a neutral complex and two methanol mol-ecules. In the complex, the two tridentate 2-(3-(4-chloro-phen-yl)-1-1,2,4-triazol-5-yl)-6-(1-pyrazol-1-yl)pyridine ligands coordinate to the central Ni ion through the N atoms of the pyrazole, pyridine and triazole groups, forming a pseudo-octa-hedral coordination sphere. Neighbouring tapered mol-ecules are linked through weak C-H(pz)⋯π(ph) inter-actions into monoperiodic chains, which are further linked through weak C-H⋯N/C inter-actions into diperiodic layers.

Crystal structure of polymeric bis-(3-amino-1-pyrazole)-cadmium diiodide.

The reaction of cadmium iodide with 3-amino-pyrazole (3-apz) in ethano-lic solution leads to tautomerization of the ligand and the formation of crystals of the title compound, -poly[[di-iodido-cadmium(II)]-bis-(μ-3-amino-1-pyrazole)-κ : ;κ : ], [CdI(CHN)] or [CdI(3-apz)] . Its asymmetric unit consists of a half of a Cd cation, an iodide anion and a 3-apz mol-ecule. The Cd cations are coordinated by two iodide anions and two 3-apz ligands, generating -CdNI octa-hedra, which are linked into chains by pairs of the bridging ligands.

Rotational order-disorder and spin crossover behaviour in a neutral iron(II) complex based on asymmetrically substituted large planar ionogenic ligand.

Octahedrally coordinated spin crossover (SCO) Fe complexes represent an important class of switchable molecular materials. This study presents the synthesis and characterisation of a novel complex, [Fe(ppt-2Fph)]·2MeOH, where ppt-2Fph is a new asymmetric ionogenic tridentate planar ligand 2-(5-(2-fluorophenyl)-4-1,2,4-triazol-3-yl)-6-(1-pyrazol-1-yl)pyridine. The complex exhibits a hysteretic thermally induced SCO transition at 285 K on cooling and at 293 K on heating, as well as light induced excited spin state trapping (LIESST) at lower temperatures with a relaxation (LIESST) temperature of 73 K.

Crystal structure of polymeric bis-(3-amino-1-pyrazole)-cadmium dibromide.

The reaction of cadmium bromide tetra-hydrate with 3-amino-pyrazole (3-apz) in ethano-lic solution leads to tautomerization of the ligand and the formation of crystals of the title compound, -poly[[di-bromido-cadmium(II)]-bis-(μ-3-amino-1-pyrazole)-κ : ;κ : ], [CdBr(CHN)] or [CdBr(3-apz)]. Its asymmetric unit consists of a half of a Cd cation, a bromide anion and a 3-apz mol-ecule. The Cd cations are coordinated by two bromide anions and two 3-apz ligands, generating -CdNBr octa-hedra, which are linked into chains by pairs of the bridging ligands.

Design and Processing as Ultrathin Films of a Sublimable Iron(II) Spin Crossover Material Exhibiting Efficient and Fast Light-Induced Spin Transition.

Materials based on spin crossover (SCO) molecules have centered the attention in molecular magnetism for more than 40 years as they provide unique examples of multifunctional and stimuli-responsive materials, which can be then integrated into electronic devices to exploit their molecular bistability. This process often requires the preparation of thermally stable SCO molecules that can sublime and remain intact in contact with surfaces. However, the number of robust sublimable SCO molecules is still very scarce.

Crystal structure of bis-{3-(3,4-di-meth-oxy-phen-yl)-5-[6-(pyrazol-1-yl)pyridin-2-yl]-1,2,4-triazol-3-ato}iron(II)-methanol-chloro-form (1/2/2).

The unit cell of the title compound, [Fe(CHNO)]·2CHOH·2CHCl, consists of a charge-neutral complex mol-ecule, two methanol and two chloro-form mol-ecules. In the complex, the two tridentate 2-(5-(3,4-di-meth-oxy-phen-yl)-1,2,4-triazol-3-yl)-6-(pyrazol-1-yl)pyridine ligands coordinate to the central Fe ion through the N atoms of the pyrazole, pyridine and triazole groups, forming a pseudo-octa-hedral coordination sphere. Neighbouring tapered mol-ecules are linked through weak C-H(pz)⋯π(ph) inter-actions into one-dimensional chains, which are joined into two-dimensional layers through weak C-H⋯N/C/O inter-actions.

Spin-Crossover and Fragmentation of Fe(neoim) on Silver and Gold.

The neutral spin crossover complex Fe(neoim), neoim being the deprotonated form of the ionogenic ligand 2-(1-imidazol-2-yl)-9-methyl-1,10-phenanthroline (neoimH), is investigated on the (111) surfaces of Au and Ag using scanning tunneling microscopy and density functional theory calculations. The complex sublimates and adsorbs intact on Ag(111), where it exhibits an electron-induced spin crossover. However, it fragments on Au.

Order-Disorder, Symmetry Breaking, and Crystallographic Phase Transition in a Series of Bis(-thiocyanate)iron(II) Spin Crossover Complexes Based on Tetradentate Ligands Containing 1,2,3-Triazoles.

We report herein a series of neutral -thiocyanate mononuclear spin crossover (SCO) complexes, [FeL(NCS)] (-), based on tetradentate ligands L obtained by reaction of N-substituted 1,2,3-triazolecarbaldehyde with 1,3-propanediamine or 2,2-dimethyl-1,3-diaminopropane [L = ,-bis((1,5-dimethyl-1-1,2,3-triazol-4-yl)methylene)propane-1,3-diamine/-2,2-dimethylpropane-1,3-diamine, / and ,-bis((1-ethyl/1-propyl-1-1,2,3-triazol-4-yl)methylene)-2,2-dimethylpropane-1,3-diamine, /]. The thermal-induced SCO behavior is characterized by abrupt transitions with an average critical temperature (Δ)/hysteresis loop width (Δ) in the range 190-252/5-14 K, while the photo-generated metastable high-spin (HS) phases are characterized by temperatures in the range 44-59 K. Single crystal analysis shows that except , all compounds experience reversible symmetry breaking coupled with the thermal SCO.

Crystal structure of bis-{3-(3,4-di-methyl-phen-yl)-5-[6-(1-pyrazol-1-yl)pyridin-2-yl]-4-1,2,4-triazol-4-ido}iron(II) methanol disolvate.

As a result of the high symmetry of the 2 structure, the asymmetric unit of the title compound, [Fe(CHN)]·2MeOH, consists of half of a charge-neutral complex mol-ecule and a discrete methanol mol-ecule. The planar anionic tridentate ligand 2-[5-(3,4-di-methyl-phen-yl)-4-1,2,4-triazol-3-ato]-6-(1-pyrazol-1-yl)pyridine coordinates the Fe ion meridionally through the N atoms of the pyrazole, pyridine and triazole groups, forming a pseudo-octa-hedral coordination sphere of the central ion. The average Fe-N bond distance is 1.

Crystal structure of bis-{3-(3-bromo-4-methoxyphenyl)-5-[6-(1-pyrazol-1-yl)pyridin-2-yl]-1,2,4-triazol-3-ato}-iron(II) methano-l disolvate.

The unit cell of the title compound, [Fe(CHBrNO)]·2MeOH, consists of a charge-neutral complex mol-ecule and two independent mol-ecules of methanol. In the complex mol-ecule, the two tridentate ligand mol-ecules 2-[5-(3-bromo-4-meth-oxy-phen-yl)-4-1,2,4-triazol-3-yl]-6-(1-pyrazol-1-yl)pyridine coordinate to the Fe ion through the N atoms of the pyrazole, pyridine and triazole groups, forming a pseudo-octa-hedral coordination sphere around the central ion. In the crystal, neighbouring asymmetric mol-ecules are linked through weak C-H(pz)⋯π(ph) inter-actions into chains, which are then linked into layers by weak C-H⋯N/C inter-actions.

105 K Wide Room Temperature Spin Transition Memory Due to a Supramolecular Latch Mechanism.

Little is known about the mechanisms behind the bistability (memory) of molecular spin transition compounds over broad temperature ranges (>100 K). To address this point, we report on a new discrete Fe neutral complex [FeL] () based on a novel asymmetric tridentate ligand 2-(5-(3-methoxy-4-1,2,4-triazol-3-yl)-6-(1-pyrazol-1-yl))pyridine (L). Due to the asymmetric cone-shaped form, in the lattice, the formed complex molecules stack into a one-dimensional (1D) supramolecular chain.

Crystal structure and Hirshfeld surface analysis of the anionic tetra-kis-complex of lanthanum(III) NMeLa with the CAPh-ligand dimeth-yl (2,2,2-tri-chloro-acet-yl)phospho-ramidate.

The anionic tetra-kis-complex of lanthanum(III) NMeLa with the CAPh-ligand dimethyl (2,2,2-tri-chloro-acet-yl)phospho-ramidate (H), namely, tetra-methyl-ammonium tetra-kis-{2,2,2-tri-chloro-1-[(di-meth-oxy-phosphor-yl)imino]-ethano-lato}lanthanum(III), (CHN)[La(CHClNOP)], has been synthesized, crystallized and structurally characterized by X-ray diffraction. The lanthanide ion is surrounded by four anionic, bis-chelating CAPh ligands forming the complex anion with a coordination number of eight for La and NMe as the counter-ion. The coordination polyhedron of the La ion was inter-preted as a triangular dodeca-hedron.

Guest induced reversible on-off switching of elastic frustration in a 3D spin crossover coordination polymer with room temperature hysteretic behaviour.

A binary reversible switch between low-temperature multi-step spin crossover (SCO), through the evolution of the population () with high-spin (HS)-low-spin (LS) sequence: HSLS (state 1) ↔ HSLS (state 2) ↔ HSLS (state 3) ↔ HSLS (state 4) ↔ HSLS (state 5), and complete one step hysteretic spin transition featuring 20 K wide thermal hysteresis centred at 290 K occurs in the three-dimensional (3D) Hofmann-type porous coordination polymer {Fe(3,8phen)[Au(CN)]}·PhNO (3,8phen = 3,8-phenanthroline, PhNO = nitrobenzene), made up of two identical interpenetrated pcu-type frameworks. The included PhNO guest ( = 1, ) acts as a molecular wedge between the interpenetrated 3D frameworks PhNO-3,8phen intermolecular recognition and is the source of the strong elastic frustration responsible for the multi-step regime. Detailed X-ray single crystal analysis reflects competition between spatial periodicities of structurally inequivalent HS and LS SCO centres featuring: (i) symmetry breaking (state 3) with ⋯HS-LS⋯ ordering with = 1/2; and (ii) occurrence of spatial modulation of the structure providing evidence for stabilization of local or aperiodic ordered mixed spin states for states 2 and 4 (with ≈ 2/3) and 4 (with ≈ 1/3), respectively.

Crystal structure of { , -bis-[(1--butyl-1-1,2,3-triazol-4-yl)methyl-idene]-2,2-di-methyl-propane-1,3-di-amine}-bis-(thio-cyanato)-iron(II).

The unit cell of the title compound, [Fe(NCS)(CHN)], consists of two charge-neutral complex mol-ecules. In the complex mol-ecule, the tetra-dentate ligand -bis-[(1--butyl-1-1,2,3-triazol-4-yl)methyl-ene]-2,2-di-methyl-propane-1,3-di-amine coordinates to the Fe ion through the N atoms of the 1,2,3-triazole and aldimine groups. Two thio-cyanate anions, also coordinated through their N atoms, complete the coordination sphere of the central Fe ion.

Crystal structure of ( , -bis-{[1-(4-meth-oxy-benz-yl)-1-1,2,3-triazol-4-yl]methyl-idene}-2,2-di-meth-yl-propane-1,3-di-amine)-bis-(thio-cyanato)-iron(II).

The unit cell of the title compound, [Fe(NCS)(CHNO)], consists of eight charge-neutral complex mol-ecules. In the complex mol-ecule, the tetra-dentate ligand , -bis-{[1-(4-meth-oxy-benz-yl)-1-1,2,3-triazol-4-yl]methyl-ene}-2,2-di-methyl-propane-1,3-di-amine coordinates to the Fe ion through the N atoms of the 1,2,3-triazole and aldimine groups. Two thio-cyanate anions, coordinated through their N atoms, complete the coordination sphere of the central Fe ion.

Crystal structure of { , -bis-[(1-benzyl-1-1,2,3-triazol-4-yl)methyl-idene]-2,2-di-methyl-propane-1,3-di-amine}bis-(thio-cyanato-κ)iron(II).

The unit cell of the title compound, [Fe(NCS)(CHN)], consists of two charge-neutral complex mol-ecules related by an inversion centre. In the complex mol-ecule, the tetra-dentate ligand , -bis-[(1-benzyl-1-1,2,3-triazol-4-yl)methyl-ene]-2,2-di-methyl-propane-1,3-di-amine coordinates to the Fe ion through the N atoms of the 1,2,3-triazole moieties and aldimine groups. Two thio-cyanate anions, coordinating through their N atoms, complete the coordination sphere of the central ion.

Thermochromic Meltable Materials with Reverse Spin Transition Controlled by Chemical Design.

We report a series of meltable Fe complexes, which, depending on the length of aliphatic chains, display abrupt forward low-spin to high-spin transition or unprecedented melting-triggered reverse high-spin to low-spin transition on temperature rise. The reverse spin transition is perfectly reproducible on thermal cycling and the obtained materials are easily processable in the form of thin film owing to their soft-matter nature. We found that the discovered approach represents a potentially generalizable new avenue to control both the location in temperature and the direction of the spin transition in meltable compounds.

Variable Cooperative Interactions in the Pressure and Thermally Induced Multistep Spin Transition in a Two-Dimensional Iron(II) Coordination Polymer.

Two types of experiments conducted to investigate the effect of pressure on the spin crossover (SCO) properties of the 2D Fe(II) coordination polymer formulated {Fe[bipy(ttr)]} are reported, namely, (1) magnetic measurements performed at variable temperature and at fixed pressure and (2) visible spectroscopy at variable pressure and fixed temperature. The magnetic experiments carried out under a hydrostatic pressure constraint of 0.04, 0.

Crystal structure of the mixed methanol and ethanol solvate of bis-{3,4,5-trimeth-oxy-'-[1-(pyridin-2-yl)ethyl-idene]benzohydrazidato}zinc(II).

The unit cell of the title compound, [Zn(CHNO)]·CHO·CHO, contains two complex mol-ecules related by an inversion centre, plus one methanol and one ethanol solvent molecule per complex molecule. In each complex, two deprotonated pyridine aroylhydrazone ligands {3,4,5-trimeth-oxy-'-[1-(pyridin-2-yl)ethyl-idene]benzohydrazide} coordinate to the Zn ion through the N atoms of the pyridine group and the ketamine, and, additionally, through the O atom of the enolate group. In the crystal, dimers are formed by π-π inter-actions between the planar ligand moieties, which are further connected by C⋯O and C⋯C inter-actions.

Crystal structure and magnetic properties of bis-[butyl-tris-(1-pyrazol-1-yl)borato]iron(II).

The asymmetric unit of the title compound, [Fe(CHBN)], contains two half independent complex mol-ecules. In each complex, the Fe atom is located on an inversion center and is surrounded by two scorpionate ligand butyl-tris-(1-pyrazol-1-yl)borate mol-ecules that coordinate to the iron(II) ion through the N atoms of the pyrazole groups. The two independent complex mol-ecules differ essentially in the conformation of the butyl substituents.

Discrimination between two memory channels by molecular alloying in a doubly bistable spin crossover material.

A multistable spin crossover (SCO) molecular alloy system [Fe M (Bu-im)(tren)](P As F) (M = Zn, Ni; (Bu-im)(tren) = tris(-butyl-imidazol(2-ethylamino))amine) has been synthesized and characterized. By controlling the composition of this isomorphous series, two cooperative thermally induced SCO events featuring distinct critical temperatures ( ) and hysteresis widths (Δ , memory) can be selected at will. The pristine derivative 100As ( = 0, = 1) displays a strong cooperative two-step SCO and two reversible structural phase transitions (PTs).

Synthesis and Characterization of Anionic Lanthanide(III) Complexes with a Bidentate Sulfonylamidophosphate (SAPh) Ligand.

A series of new anionic lanthanide(III) complexes with the general formula NEt[Ln] (; H = dimethyl[(4-methylphenyl)sulfonyl]amidophosphate; Ln = La, Nd, Eu), were synthesized and characterized by IR, UV-vis, and NMR spectroscopies, the differential scanning calorimetry method, thermogravimetric and X-ray analysis, and photoluminescence measurements. Single-crystal structures of NEt[Eu] () were determined at 293 and 100 K and evidenced the phase transition. Both phases are in the monoclinic crystal system in centrosymmetric groups of the same Laue class.

Very Long-Lived Photogenerated High-Spin Phase of a Multistable Spin-Crossover Molecular Material.

The spin-crossover compound [Fe( n-Bu-im)(tren)](PF) shows an unusual long relaxation time of 20 h after light-induced excited spin state trapping when irradiating at 80 K. This is more than 40 times longer than when irradiating at 10 K. Optical absorption spectroscopy, magnetometry, and X-ray diffraction using synchrotron radiation were used to characterize and explain the different relaxation behaviors of this compound after irradiation below and above 70 K.

Chiral and Racemic Spin Crossover Polymorphs in a Family of Mononuclear Iron(II) Compounds.

Understanding the origin of cooperativity and the equilibrium temperature of transition (T) displayed by the spin-crossover (SCO) compounds as well as controlling these parameters are of paramount importance for future applications. For this task, the occurrence of polymorphism, presented by a number of SCO complexes, may provide deep insight into the influence of the supramolecular organization on the SCO behavior. In this context, herein we present a novel family of mononuclear octahedral Fe complexes with formula cis-[Fe(bqen)(NCX)], where bqen is the chelating tetradentate ligand N,N'-bis(8-quinolyl)ethane-1,2-diamine and X = S, Se.

Guest Induced Strong Cooperative One- and Two-Step Spin Transitions in Highly Porous Iron(II) Hofmann-Type Metal-Organic Frameworks.

The synthesis, crystal structure, magnetic, calorimetric, and Mössbauer studies of a series of new Hofmann-type spin crossover (SCO) metal-organic frameworks (MOFs) is reported. The new SCO-MOFs arise from self-assembly of Fe, bis(4-pyridyl)butadiyne (bpb), and [Ag(CN)] or [M(CN)] (M = Ni, Pd). Interpenetration of four identical 3D networks with α-Po topology are obtained for {Fe(bpb)[Ag(CN)]} due to the length of the rod-like bismonodentate bpb and [Ag(CN)] ligands.