Synthesis, crystal structure and thermal properties of catena-poly[[bis-(4-methyl-pyridine)-nickel(II)]-di-µ-thio-cyanato], which shows an alternating all-trans and cis-cis-trans-coordination of the NiS2Np 2Nt 2 octa-hedra (p = 4-methyl-pyridine, t = thio-cyanate).

The title compound, [Ni(NCS)2(C6H7N)2] n , was prepared by the reaction of Ni(NCS)2 with 4-methyl-pyridine in water. Its asymmetric unit consists of two crystallographically independent NiII cations, of which one is located on a twofold rotational axis whereas the second occupies a center of inversion, two independent thio-cyanate anions and two independent 4-methyl-pyridine co-ligands in general positions. Each NiII cation is octa-hedrally coordinated by two 4-methyl-pyridine coligands as well as two N- and two S-bonded thio-cyanate anions. One of the cations shows an all-trans, the other a cis-cis-trans configuration. The metal centers are linked by pairs of µ-1,3-bridging thio-cyanate anions into [101] chains. X-ray powder diffraction shows that a pure crystalline phase has been obtained and thermogravimetry coupled to differential thermoanalysis reveals that the title compound loses half of the 4-methyl-pyridine coligands and transforms into Ni(NCS)2(C6H7N). Nearly pure samples of this compound can be obtained by thermal annealing and a Rietveld refinement demonstrated that it is isotypic to its recently reported Cd analog [Neumann et al., (2020 ▸). CrystEngComm. 22, 184-194] In its crystal structure, the metal cations are linked by one µ-1,3(N,S)- and one µ-1,3,3(N,S,S)-bridging thio-cyanate anion into single chains that condense via the µ-1,3,3(N,S,S)-bridging anionic ligands into double chains.

Syntheses and crystal structures of the five- and sixfold coordinated complexes diiso-seleno-cyanato-tris-(2-methyl-pyridine N-oxide)cobalt(II) and diiso-seleno-cyanato-tetra-kis-(2-methyl-pyridine N-oxide)cobalt(II).

The reaction of CoBr2, KNCSe and 2-methyl-pyridine N-oxide (C6H7NO) in ethanol leads to the formation of crystals of [Co(NCSe)2(C6H7NO)3] (1) and [Co(NCSe)2(C6H7NO)4] (2) from the same reaction mixture. The asymmetric unit of 1 is built up of one CoII cation, two NCSe- iso-seleno-cyanate anions and three 2-methyl-pyridine N-oxide coligands, with all atoms located on general positions. The asymmetric unit of 2 consists of two cobalt cations, four iso-seleno-canate anions and eight 2-methyl-pyridine N-oxide coligands in general positions, because two crystallographically independent complexes are present. In compound 1, the CoII cations are fivefold coordinated to two terminally N-bonded anionic ligands and three 2-methyl-pyridine N-oxide coligands within a slightly distorted trigonal-bipyramidal coordination, forming discrete complexes with the O atoms occupying the equatorial sites. In compound 2, each of the two complexes is coordinated to two terminally N-bonded iso-seleno-cyanate anions and four 2-methyl-pyridine N-oxide coligands within a slightly distorted cis-CoN2O4 octa-hedral coordination geometry. In the crystal structures of 1 and 2, the complexes are linked by weak C-H⋯Se and C-H⋯O contacts. Powder X-ray diffraction reveals that neither of the two compounds were obtained as a pure crystalline phase.

Synthesis, crystal structure and thermal properties of a new polymorphic modification of diiso-thio-cyanato-tetra-kis-(4-methyl-pyridine)cobalt(II).

The title compound, [Co(NCS)2(C6H7N)4] or Co(NCS)2(4-methyl-pyridine)4, was prepared by the reaction of Co(NCS)2 with 4-methyl-pyridine in water and is isotypic to one of the polymorphs of Ni(NCS)2(4-methyl-pyridine)4 [Kerr & Williams (1977 ▸). Acta Cryst. B33, 3589-3592 and Soldatov et al. (2004 ▸). Cryst. Growth Des. 4, 1185-1194]. Comparison of the experimental X-ray powder pattern with that calculated from the single-crystal data proves that a pure phase has been obtained. The asymmetric unit consists of one CoII cation, two crystallographically independent thio-cyanate anions and four independent 4-meth-yl-pyridine ligands, all located in general positions. The CoII cations are sixfold coordinated to two terminally N-bonded thio-cyanate anions and four 4-methyl-pyridine coligands within slightly distorted octa-hedra. Between the complexes, a number of weak C-H⋯N and C-H⋯S contacts are found. This structure represent a polymorphic modification of Co(NCS)2(4-methyl-pyridine)4 already reported in the CCD [Harris et al. (2003 ▸). NASA Technical Reports, 211890]. In contrast to this form, the crystal structure of the new polymorph shows a denser packing, indicating that it is thermodynamically stable at least at low temperatures. Thermogravimetric and differential thermoanalysis reveal that the title compound starts to decomposes at about 100°C and that the coligands are removed in separate steps without any sign of a polymorphic transition before decomposition.

Synthesis, crystal structure and properties of the trigonal-bipyramidal complex tris-(2-methyl-pyridine N-oxide-κO)bis-(thio-cyanato-κN)cobalt(II).

Reaction of Co(NCS)2 with 2-methyl-pyridine N-oxide in a 1:3 ratio in n-butanol leads to the formation of crystals of tris-(2-methyl-pyridine N-oxide-κO)bis-(thio-cyanato-κN)cobalt(II), [Co(NCS)2(C6H7NO)3]. The asymmetric unit of the title compound consists of one CoII cation two thio-cyanate anions and three crystallographically independent 2-methyl-pyridine N-oxide coligands in general positions. The CoII cations are trigonal-bipyramidally coordinated by two terminal N-bonding thio-cyanate anions in the trans-positions and three 2-methyl-pyridine N-oxide coligands into discrete complexes. These complexes are linked by inter-molecular C-H⋯S inter-actions into double chains that elongate in the c-axis direction. Powder X-ray diffraction (PXRD) measurements prove that all batches are always contaminated with an additional and unknown crystalline phase. Thermogravimetry and differential analysis of crystals selected by hand reveal that the title compound decomposes at about 229°C in an exothermic reaction. At about 113°C a small endothermic signal is observed that, according to differential scanning calorimetry (DSC) measurements, is irreversible. PXRD measurements of the residue prove that a poorly crystalline and unknown phase has formed and thermomicroscopy indicates that some phase transition occurs that is accompanied with a color change of the title compound.

Synthesis, crystal structure and thermal properties of the dinuclear complex bis-(µ-4-methylpyridine N-oxide-κ2O:O)bis-[(methanol-κO)(4-methylpyridine N-oxide-κO)bis-(thio-cyanato-κN)cobalt(II)].

Reaction of Co(NCS)2 with 4-methyl-pyridine N-oxide in methanol leads to the formation of crystals of the title compound, [Co2(NCS)4(C6H7NO)4(CH4O)2] or Co2(NCS)4(4-methyl-pyridine N-oxide)4(methanol)2. The asymmetric unit consist of one CoII cation, two thio-cyanate anions, two 4-methyl-pyridine N-oxide coligands and one methanol mol-ecule in general positions. The H atoms of one of the methyl groups are disordered and were refined using a split model. The CoII cations octa-hedrally coordinate two terminal N-bonded thio-cyanate anions, three 4-methyl-pyridine N-oxide coligands and one methanol mol-ecule. Each two CoII cations are linked by pairs of µ-1,1(O,O)-bridging 4-methyl-pyridine N-oxide coligands into dinuclear units that are located on centers of inversion. Powder X-ray diffraction (PXRD) investigations prove that the title compound is contaminated with a small amount of Co(NCS)2(4-meth-yl-pyridine N-oxide)3. Thermogravimetric investigations reveal that the methanol mol-ecules are removed in the beginning, leading to a compound with the composition Co(NCS)2(4-methyl-pyridine N-oxide), which has been reported in the literature and which is of poor crystallinity.

Synthesis and crystal structure of tetra-methyl (E)-4,4'-(ethene-1,2-di-yl)bis-(5-nitro-benzene-1,2-di-carboxyl-ate).

The title compound, C22H18N2O12, was obtained as a by-product during the planned synthesis of 1,2-bis-(2-nitro-4,5-dimethyl phthalate)ethane by oxidative dimerization starting from dimethyl-4-methyl-5-nitro phthalate. To identify this compound unambiguously, a single-crystal structure analysis was performed. The asymmetric unit consists of half a mol-ecule that is located at a centre of inversion. As a result of symmetry restrictions, the mol-ecule shows an E configuration around the double bond. Both phenyl rings are coplanar, whereas the nitro and the two methyl ester groups are rotated out of the ring plane by 32.6 (1), 56.5 (2) and 49.5 (2)°, respectively. In the crystal, mol-ecules are connected into chains extending parallel to the a axis by pairs of C-H⋯O hydrogen bonds that are connected into a tri-periodic network by additional C-H⋯O hydrogen-bonding inter-actions.

Expanding the Chemical Space of Transforming Growth Factor-ß (TGFß) Receptor Type II Degraders with 3,4-Disubstituted Indole Derivatives.

The TGFß type II receptor (TßRII) is a central player in all TGFß signaling downstream events, has been linked to cancer progression, and thus, has emerged as an auspicious anti-TGFß strategy. Especially its targeted degradation presents an excellent goal for effective TGFß pathway inhibition. Here, cellular structure-activity relationship (SAR) data from the TßRII degrader chemotype 1 was successfully transformed into predictive ligand-based pharmacophore models that allowed scaffold hopping. Two distinct 3,4-disubstituted indoles were identified from virtual screening: tetrahydro-4-oxo-indole 2 and indole-3-acetate 3. Design, synthesis, and screening of focused amide libraries confirmed 2r and 3n as potent TGFß inhibitors. They were validated to fully recapitulate the ability of 1 to selectively degrade TßRII, without affecting TßRI. Consequently, 2r and 3n efficiently blocked endothelial-to-mesenchymal transition and cell migration in different cancer cell lines while not perturbing the microtubule network. Hence, 2 and 3 present novel TßRII degrader chemotypes that will (1) aid target deconvolution efforts and (2) accelerate proof-of-concept studies for small-molecule-driven TßRII degradation in vivo.

Synthesis, crystal structure and properties of poly[(µ-2-methyl-pyridine N-oxide-κ2O:O)bis-(µ-thio-cyanato-κ2N:S)cobalt(II)].

The title compound, [Co(NCS)2(C6H7NO)]n or Co(NCS)2(2-methyl-pyridine N-oxide), was prepared by the reaction of Co(NCS)2 and 2-methyl-pyridine N-oxide in methanol. All crystals obtained by this procedure show reticular pseudo-merohedric twinning, but after recrystallization, one crystal was found that had a minor component with only a very few overlapping reflections. The asymmetric unit consists of one CoII cation, two thio-cyanate anions and one 2-methyl-pyridine N-oxide coligand in general positions. The CoII cations are octa-hedrally coordinated by two O-bonding 2-methyl-pyridine N-oxide ligands, as well as two S- and two N-bonding thio-cyanate anions, and are connected via µ-1,3(N,S)-bridging thio-cyanate anions into chains that are linked by µ-1,1(O,O) bridging coligands into layers. No pronounced directional inter-molecular inter-actions are observed between the layers. The 2-methyl-pyridine coligand is disordered over two orientations and was refined using a split model with restraints. Powder X-ray diffraction (PXRD) indicates that a pure sample was obtained and IR spectroscopy confirms that bridging thio-cyanate anions are present. Thermogravimetry and differential thermoanalysis (TG-DTA) shows one poorly resolved mass loss in the TG curve that is accompanied by an exothermic and an endothermic signal in the DTA curve, which indicate the decomposition of the 2-methyl-pyridine N-oxide coligands.

Molybdenum(0)-Tricarbonyl Complex Supported by an Azacalix-pyridine Ligand: Synthesis, Characterization, Surface Deposition and Conversion to a Molybdenum(VI)-Trioxo Complex with O2.

Adsorption of metal-organic complexes on metallic surfaces to produce well-defined single site catalysts is a novel approach combining the advantages of homogeneous and heterogeneous catalysis. To avoid the "surface trans-effect" a dome-shaped molybdenum(0) tricarbonyl complex supported by an tolylazacalix[3](2,6)pyridine ligand is synthesized. This vacuum-evaporable complex both activates CO and reacts with molecular oxygen (O2) to form a Mo(VI) trioxo complex which in turn is capable of catalytically mediating oxygen transfer. The molybdenum tricarbonyl- and trioxo complexes are investigated in the solid state, in homogeneous solution and on noble metal surfaces (Cu, Au) employing a range of spectroscopic and analytical methods.

Synthesis and crystal structure of diiso-thio-cyanato-tetra-kis-(4-methyl-pyridine N-oxide)cobalt(II) and diiso-thio-cyanato-tris-(4-methyl-pyridine N-oxide)cobalt(II) showing two different metal coordination polyhedra.

The reaction of Co(NCS)2 with 4-methyl-pyridine N-oxide (C6H7NO) leads to the formation of two compounds, namely, tetra-kis-(4-methyl-pyridine N-oxide-κO)bis-(thio-cyanato-κN)cobalt(II), [Co(NCS)2(C6H7NO)4] (1), and tris-(4-methyl-pyridine N-oxide-κO)bis-(thio-cyanato-κN)cobalt(II), [Co(NCS)2(C6H7NO)3] (2). The asymmetric unit of 1 consists of one CoII cation located on a centre of inversion, as well as one thio-cyanate anion and two 4-methyl-pyridine N-oxide coligands in general positions. The CoII cations are octa-hedrally coordinated by two terminal N-bonding thio-cyanate anions in trans positions and four 4-methyl-pyridine N-oxide ligands. In the extended structure, these complexes are linked by C-H⋯O and C-H⋯S inter-actions. In compound 2, two crystallographically independent complexes are present, which occupy general positions. In each of these complexes, the CoII cations are coordinated in a trigonal-bipyramidal manner by two terminal N-bonding thio-cyanate anions in axial positions and by three 4-methyl-pyridine N-oxide ligands in equatorial positions. In the crystal, these complex mol-ecules are linked by C-H⋯S inter-actions. For compound 2, a nonmerohedral twin refinement was performed. Powder X-ray diffraction (PXRD) reveals that 2 was nearly obtained as a pure phase, which is not possible for compound 1. Differential thermoanalysis and thermogravimetry data (DTA-TG) show that compound 2 start to decompose at about 518 K.

Synthesis, crystal structure and thermal properties of di-bromido-bis-(2-methyl-pyridine N-oxide-κO)cobalt(II).

Reaction of CoBr2 with 2-methyl-pyridine N-oxide in n-butanol leads to the formation of the title compound, [CoBr2(C6H7NO)2] or [CoBr2(2-methyl-pyridine N-oxide)2]. Its asymmetric unit consists of one CoII cation as well as two bromide anions and two 2-methyl-pyridine N-oxide coligands in general positions. The CoII cations are tetra-hedrally coordinated by two bromide anions and two 2-methyl-pyridine N-oxides, forming discrete complexes. In the crystal structure, these complexes are linked predominantly by weak C-H⋯Br hydrogen bonding into chains that propagate along the crystallographic a-axis. Powder X-ray diffraction (PXRD) measurements indicate that a pure phase was obtained. Thermoanalytical investigations prove that the title compound melts before decomposition; before melting, a further endothermic signal of unknown origin was observed that does not correspond to a phase transition.

Synthesis, crystal structure and thermal properties of poly[[µ-1,2-bis-(pyridin-4-yl)ethene-κ2N:N'-µ-bromido-copper(I)] 1,2-bis-(pyridin-4-yl)ethene 0.25-solvate].

The reaction of copper(I) bromide with 1,2-bis-(pyridin-4-yl)ethene in aceto-nitrile leads to the formation of the title compound, {[CuBr(C12H10N2)]·0.25C12H10N2}n or CuBr(4-bpe)·0.25(4-bpe) [4-bpe = 1,2-bis-(pyridin-4-yl)ethene]. The asymmetric unit consists of one copper(I) cation and one bromide anion in general positions as well as two crystallographically independent half 4-bpe ligands and a quarter of a disordered 4-bpe solvate mol-ecule that are completed by centers of inversion. The copper(I) cations are tetra-hededrally coordinated as CuBr2N2 and linked by pairs of µ-1,1-bridging bromide anions into centrosymmetric dinuclear units that are further connected into layers by the 4-bpe coligands. Between the layers, inter-layer C-H⋯Br hydrogen bonding is observed. The layers are arranged in such a way that cavities are formed in which the disordered 4-bpe solvate mol-ecules are located. Powder X-ray (PXRD) investigations reveal that a pure sample has been obtained. Thermogravimetric (TG) and differential thermoanalysis (DTA) measurements show two mass losses that are accompanied by endothermic events in the DTA curve. The first mass loss correspond to the removal of 0.75 4-bpe mol-ecules, leading to the formation of (CuBr)2(4-bpe), already reported in the literature as proven by PXRD.

Synthesis, crystal structure and reactivity of bis-(µ-2-methyl-pyridine N-oxide-κ2O:O)bis-[di-bromido-(2-methyl-pyridine N-oxide-κO)cobalt(II)] butanol monosolvate.

Reaction of CoBr2 with 2-methyl-pyridine N-oxide in n-butanol leads to the formation of the title compound, [CoBr2]2(2-methyl-pyridine N-oxide)4·n-butanol or [Co2Br4(C6H7NO)4]·C4H10O. The asymmetric unit of the title compound consists of one CoII cation as well as two bromide anions and two 2-methyl-pyridine N-oxide coligands in general positions and one n-butanol mol-ecule that is disordered around a center of inversion. The CoII cations are fivefold coordinated by two bromide anions and one terminal as well as two bridging 2-methyl-pyridine N-oxide and linked by two symmetry-related µ-1,1(O,O) 2-methyl-pyridine N-oxide coligands into dinuclear units that are located on centers of inversion. In the crystal structure, the dinuclear units are also connected via pairs of C-H⋯Br hydrogen bonds into chains that elongate in the b-axis direction. The n-butanol mol-ecules are located between the chains and are linked via O-H⋯Br hydrogen bonds each to one chain. Powder X-ray diffraction (PXRD) measurements reveal that a pure phase has been obtained. Measurements using thermogravimetry and differential thermoanalysis shows one mass loss up to 523 K, in which the n-butanol mol-ecules are removed. PXRD measurements of the residue obtained after n-butanol removal shows that a completely different crystalline phase has been obtained and IR investigations indicate significant structural changes in the Co coordination.

Synthesis, crystal structure and properties of tetra-kis-(pyridine-3-carbo-nitrile)-dithio-cyanatoiron(II) and of diaqua-bis-(pyridine-3-carbo-nitrile)-di-thio-cyanatoiron(II) pyridine-3-carbo-nitrile monosolvate.

The reaction of iron thio-cyanate with 3-cyano-pyridine (C6H4N2) leads to the formation of two compounds with the composition [Fe(NCS)2(C6H4N2)4] (1) and [Fe(NCS)2(C6H4N2)2(H2O)2]·2C6H4N2 (2). The asymmetric unit of 1 consists of one iron cation, two thio-cyanate anions and four 3-cyano-pyridine ligands in general positions. The iron cation is octa-hedrally coordinated by two N-bonded thio-cyanate anions and four 3-cyano-pyridine ligands. The complexes are arranged in columns along the crystallographic c-axis direction and are linked by weak C-H⋯N inter-actions. In 2, the asymmetric unit consists of one iron cation on a center of inversion as well as one thio-cyanate anion, one 3-cyano-pyridine ligand, one water ligand and one 3-cyano-pyridine solvate mol-ecule in general positions. The iron cation is octa-hedrally coordinated by two N-bonded thio-cyanate anions, two cyano-pyridine ligands and two water ligands. O-H⋯N and C-H⋯S hydrogen bonding is observed between the water ligands and the solvent 3-cyano-pyridine mol-ecules. In the crystal structure, alternating layers of the iron complexes and the solvated 3-cyano-pyridine mol-ecules are observed. Powder X-ray (PXRD) investigations reveal that both compounds were obtained as pure phases and from IR spectroscopic measurements conclusions on the coordination mode of the thio-canate anions and the cyano-group were made. Thermogravimetric (TG) and differential thermoanalysis (DTA) of 1 indicate the formation of a compound with the composition {[Fe(NCS)2]3(C6H4N2)4}n that is isotypic to the corresponding Cd compound already reported in the literature. TG/DTA of 2 show several mass losses. The first mass loss corresponds to the removal of the two water ligands leading to the formation of 1, which transforms into {[Fe(NCS)2]3(C6H4N2)4}n, upon further heating.

Synthesis, crystal structure and thermal behavior of tetra-kis-(3-cyano-pyridine N-oxide-κO)bis-(thio-cyanato-κN)cobalt(II), which shows strong pseudo-symmetry.

The title compound, [Co(SCN)2(C6H4N2O)4], was prepared by the reaction of cobalt(II)thio-cyanate with 3-cyano-pyridine N-oxide in ethanol. In the crystal, the cobalt(II) cations are octa-hedrally coordinated by two terminal N-bonded thio-cyanate anions and four O-bonded 3-cyano-pyridine N-oxide coligands, forming discrete complexes that are located on centers of inversion, hence forming trans-CoN2O4 octa-hedra. The structure refinement was performed in the monoclinic space group P21/n, for which a potential lattice translation and new symmetry elements with a fit of 100% is suggested. The structure can easily be refined in the space group I2/m, where the complexes have 2/m symmetry. However, nearly all of the reflections that violate the centering are observed with significant intensity and the refinement in P21/n leads to significantly lower R(F) values (0.027 versus 0.033). Moreover, in I2/m much larger components of the anisotropic displacement parameters are observed and therefore, the crystal structure is presented in the primitive unit cell. IR investigations confirm that the anionic ligands are only terminally bonded and that the cyano group is not involved in the metal coordination. PXRD investigations show that a pure crystalline phase has been obtained and measurements using simultaneously thermogravimetry and differential thermoanalysis reveal that the compound decomposes in an exothermic reaction upon heating, without the formation of a coligand-deficient inter-mediate phase.

Synthesis and crystal structure of catena-poly[cobalt(II)-di-µ-chlorido-µ-pyridazine-κ2N1:N2].

The reaction of cobalt dichloride hexa-hydrate with pyridazine leads to the formation of crystals of the title compound, [CoCl2(C4H4N2)]n. This compound is isotypic to a number of compounds with other divalent metal ions. Its asymmetric unit consists of a Co2+ atom (site symmetry 2/m), a chloride ion (site symmetry m) and a pyridazine mol-ecule (all atoms with site symmetry m). The Co2+ cations are coordinated by four chloride anions and two pyridazine ligands, generating trans-CoN4Cl2 octa-hedra, and are linked into [010] chains by pairs of µ-1,1-bridging chloride anions and bridging pyridazine ligands. In the crystal structure, the pyridazine ligands of neighboring chains are stacked onto each other, indicating π-π inter-actions. Powder X-ray diffraction proves that a pure crystalline phase was obtained. Differential thermonalysis coupled to thermogravimetry (DTA-TG) reveal that decomposition is observed at about 710 K. Magnetic measurements indicate low-temperature metamagnetic behavior as already observed in a related compound.

Tuning the spin-crossover properties of FeII4L6 cages via the interplay of coordination motif and linker modifications.

Despite the increasing number of spin-crossover FeII-based cages, the interplay between ligand modifications (e.g. coordination motif substituents and linker) is not well-understood in these multinuclear systems, limiting rational design. Here, we report a family of FeII4L6 spin-crossover cages based on 2,2'-pyridylbenzimidazoles where subtle ligand modifications lowered the spin crossover temperature in CD3CN by up to 186 K. Comparing pairs of cages, CH3 substituents on either the coordination motif or phenylene linker lowered the spin-crossover temperature by 48 K, 91 K or 186 K, attributed to electronic effects, steric effects and a combination of both, respectively. The understanding of the interplay between ligand modifications gained from this study could be harnessed on the path towards the improved rational design of spin-crossover cages.

Defying the inverse energy gap law: a vacuum-evaporable Fe(ii) low-spin complex with a long-lived LIESST state.

The novel vacuum-evaporable complex [Fe(pypypyr)2] (pypypyr = bipyridyl pyrrolide) was synthesised and analysed as bulk material and as a thin film. In both cases, the compound is in its low-spin state up to temperatures of at least 510 K. Thus, it is conventionally considered a pure low-spin compound. According to the inverse energy gap law, the half time of the light-induced excited high-spin state of such compounds at temperatures approaching 0 K is expected to be in the regime of micro- or nanoseconds. In contrast to these expectations, the light-induced high-spin state of the title compound has a half time of several hours. We attribute this behaviour to a large structural difference between the two spin states along with four distinct distortion coordinates associated with the spin transition. This leads to a breakdown of single-mode behaviour and thus drastically decreases the relaxation rate of the metastable high-spin state. These unprecedented properties open up new strategies for the development of compounds showing light-induced excited spin state trapping (LIESST) at high temperatures, potentially around room temperature, which is relevant for applications in molecular spintronics, sensors, displays and the like.

Systematic Study on Zirconium Chelidamates: From a Molecular Complex to a M-HOF and a MOF.

We report the synthesis and in-depth characterization of three zirconium chelidamates, a molecular complex (H8C2N)2[Zr(HL)3] (1), a porous metal-containing hydrogen-bonded organic framework (M-HOF) [Zr(H2O)2(HL)2]·xH2O (2), and a metal-organic framework (MOF) (H8C2N)2-2n[Zr(HnL)2]·x solvent (0 ≤ n ≤ 1) (3) using chelidamic acid (H3L, H5C7NO5, 4-hydroxypyridine-2,6-dicarboxylic acid) as the ligand (H8C2N+ = dimethylammonium). High-throughput investigations of the system Zr4+/H3L/HCl/DMF/H2O were carried out, which resulted in highly crystalline compounds. The crystal structures of 1 and 2 were determined by single-crystal X-ray diffraction. Single-crystal three-dimensional (3D) electron diffraction and Rietveld refinements of powder X-ray diffraction (PXRD) data had to be used to elucidate the crystal structure of 3 since only very small single crystals of about 500 nm in diameter could be obtained. In all structures, chelidamate ions act as anionic palindromic pincer ligands, and in 3, a coordinative bond is additionally formed by the aryloxy group. While dense packing of the molecular complexes is found in 1, hydrogen bonding of the molecular complexes in 2 leads to a porous network that shows flexibility depending on the water content. The three-dimensional framework structure of the Zr-MOF 3 contains a mononuclear inorganic building unit (IBU), which is very uncommon in Zr-MOF chemistry. The three compounds are stable in several organic solvents, and thermal decomposition starts above 280 °C. While the hydrogen-bonded framework 2 is only porous toward water with a water uptake of almost 3.75 mol mol-1 at p/p0 = 0.9, 3 is porous against N2, CO2, methanol, ethanol, and water with a specific Brunauer-Emmett-Teller (BET) surface area of aS,BET = 410 m2 g-1 derived from the N2 adsorption isotherm. Stability upon water adsorption covering 10 cycles between 0.5% < p/p0 < 90% for 3 is also demonstrated.

Weakening the Interchain Interactions in One Dimensional Cobalt(II) Coordination Polymers by Preventing Intermolecular Hydrogen Bonding.

The reaction of Co(NCS)2 with N-methylaniline leads to the formation of [Co(NCS)2(N-methylaniline)2]n (1), in which the cobalt(II) cations are octahedrally coordinated and linked into linear chains by pairs of thiocyanate anions. In contrast to [Co(NCS)2(aniline)2]n (2) reported recently, in which the Co(NCS)2 chains are linked by strong interchain N-H···S hydrogen bonding, such interactions are absent in 1. Computational studies reveal that the cobalt(II) ions in compound 1 show an easy-axis anisotropy that is lower than in 2, but with the direction of the easy axis being similar in both compounds. The high magnetic anisotropy is also confirmed by magnetic and FD-FT THz-EPR spectroscopy, which yield a consistent gz value. These investigations prove that the intrachain interactions in 1 are slightly higher than in 2. Magnetic measurements reveal that the critical temperature for magnetic ordering in 1 is significantly lower than in 2, which indicates that the elimination of the hydrogen bonds leads to a weakening of the interchain interactions. This is finally proven by FD-FT THz-EPR experiments, which show that the interchain interaction energy in the N-methylaniline compound 1 is nine-fold smaller than in the aniline compound 2.