A new pentagonal bipyramidal Fe(II) complex [FeII(H2L)(MeOH)2]Cl2·MeOH (1) with a pentadentate N3S2 chelating ligand 2,6-diacetylpyridine bis(4-N-(4-ethylphenyl)thiosemicarbazone) (H2L) was synthesized. It was found that after exposure to air, desolvation of sample 1 occurs followed by a single-crystal to single-crystal (SC-SC) transformation into the [FeII(H2L)Cl2] complex (2). Investigation of the single crystal structure revealed the loss of both crystallized and coordinated methanol, accompanied by the replacement of the latter by chlorine, which was the outer-sphere anion in structure 1. Mössbauer spectroscopy confirmed a direct conversion of 1 to 2. Such SC-SC transformations with the substitution of neutral ligands by anions and changing both the composition and charge of the resulting complex are rarely observed. The transformation of 1 into 2 becomes reversible upon dissolving complex 2 in methanol with heating, when the axial Cl- ligands are again replaced by MeOH and the growth of crystals of 1 is observed. The axial ligand substitution dramatically affects the magnetic properties of the complexes: only complex 2 demonstrates the single-ion magnet behavior in contrast to 1. The use of sulfur N3S2 analogues of oxygen N3O2 ligands leads to increasing the magnetization barrier. For a detailed analysis and comparison of magnetic properties, ab initio quantum chemical calculations were performed.

Neutral iron(III) and iron(II) complexes based on the pyruvic acid thiosemicarbazone (H2thpy) ligand [FeIII(Hthpy)(thpy)] (1) and [FeII(Hthpy)2] (2) were synthesized, and deeper insights into magneto-structural correlation were gained by FT-IR spectroscopy, single crystal X-ray crystallography, dc magnetic characterization, 57Fe Mössbauer spectroscopy, and DFT calculations. The X-ray structures of complex 1 were established for the HS (S = 5/2) state at 295 K and the LS (S = 1/2) state at 150 K. The crystal packing of 1 at these temperatures corresponds to the triclinic P1̄ symmetry and contains pairs of [FeIII(Hthpy)(thpy)] complexes interconnected by a shortened S⋯S contact. The crystal structure of 2 at 120 K is described by monoclinic I2/a symmetry and contains extended 1D chains of interconnected Fe(II) complexes in the HS (S = 2) state. According to dc magnetic measurements, a complete, abrupt spin-crossover with T1/2 = 226 K and a hysteresis loop of 8 K occurs in the temperature range of 210-240 K for complex 1, whereas complex 2 is stabilized in the HS state in the temperature range of 2-300 K. DFT calculations showed that the absence of spin-crossover for complex 2 is due to insufficient energy of splitting of d orbitals by the field of the Hthpy- ligand. BS-DFT calculations confirmed the presence of a weak antiferromagnetic exchange in the structures of 1 and 2.

Seven- and eight-coordination mononuclear complexes of Dy with the tautomeric ligand H 2 dapin in the equatorial plane and phosphinoxide ligands in axial positions have been synthesized. The PBP complex with local symmetry D 5h showed SIM behaviour with U eff = 137 K.

The hydrate of a neutral iron(III) complex based on the pyruvic acid thiosemicarbazone ligand [FeIII(Hthpy)(thpy)]·H2O (1) was synthesized and characterized using FT-IR spectroscopy, powder and single-crystal X-ray diffraction, dc magnetic measurements, EPR and 57Fe Mössbauer spectroscopy. The crystal structure of 1 was determined for the first time. Two distinct chelating ligands Hthpy- and thpy2- coordinate the Fe(III) ion to form the FeN2O2S2 octahedron which shows a low spin geometry at 150-350 K. The crystal packing contains infinite chains of the Fe(III) complexes as well as water molecules located in cavities. Along the chain, π-π interacting pairs of the Fe complexes are linked by H-bonding. According to the dc magnetic measurements, the complete abrupt spin-crossover with half-transition temperature T1/2 = 340 K and a hysteresis loop of 45 K occurs in the temperature range of 300-363 K. Based on the X-ray structure of 1, the Bleaney-Bowers equation for the isolated dimer model was used to approximate the temperature dependence of the magnetic susceptibility in the range of 2-50 K. The defined intradimer exchange constant Jexp = -0.498(1) K corresponds to a weak antiferromagnetic exchange between the iron(III) magnetic centers. DFT calculations of H- and π-π bonded fragments of the crystal structure of 1 in the HS and LS states were carried out. Moreover, BS-DFT calculations confirm the presence of antiferromagnetic exchange Jcalc = -0.92 K in the π-π bonded pairs of the ferric complexes and show the exchange pathway between Fe(III) ions by the calculated spin density distribution.

New ring silicates Cs4Tm2[Si4O12](OH)2 and Cs4(Tm,Tb)2[Si4O12](OH)2 have been synthesized by the hydrothermal method. A structural analogy is revealed between them and the previously studied silicates K4Sc2(OH)2(Si4O12) and K2Sc[Si2O6]F. Their crystal structures are identified as orthorhombic merohedral twins by the lost element of tetragonal symmetry. The structures of new ring silicates are related to those of fresnoite and tetragonal melilite.

The first molecular complexes of Cr(III) with chelating 2,6-diacetylpyridine-bis(thiosemicarbazone) Schiff-base ligand (H2daptsc), [Cr(Hdaptsc)(H2O)1.4(CH3OH)0.6](NO3)2·1.4CH3OH (1), [Cr(Hdaptsc)(H2O)2](NO3)2·1.3C2H5OH (2), [Cr(Hdaptsc)(H2O)2](NO3)2·H2O (3), [Cr(H2daptsc)(H2O)2](NO3)3·2h2O (4), [Cr(Hdaptsc)(N3)2]·CH3OH (5), [Cr(Hdaptsc)(N3)2]·1.25H2O (6) have been synthesized, and their crystal structures have been studied. Structural analysis has shown that in all the crystals, the Cr(III) cation is seven-coordinated by N3S2 atoms of the pentadentate ligand in the equatorial plane and two O or N atoms of water/methanol or N3‾ axial ligands. The pentadentate ligand is fully protonated in 4 and mono-deprotonated in one hydrazinic –NH group in all the other compounds. The degree of deprotonation depends on the pH of the reaction medium. The remaining proton in Hdaptscˉ is ordered and localized on one side of the ligand. As a result, the Hdaptscˉ ligand possesses a pronounced difference in Cr-S/N bond distances for the neutral protonated and negatively charged deprotonated halves due to the strong Jahn–Teller effect for the high-spin 3d3 configuration in the pentagonal bipyramidal (PBP) ligand field.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The iron(III) anionic complex based on a pyruvic acid thiosemicarbazone ligand with the lithium cation Li[FeIII(thpy)2]·3H2O (1) has been synthesized and characterized by FTIR spectroscopy, powder and single crystal X-ray diffraction, direct current magnetic susceptibility measurements, and 57Fe Mössbauer spectroscopy. Moreover, the molecular structure of the [Fe(thpy)2]- anion has been determined for the first time. The [Fe(thpy)2]- units in the triclinic P1̄ lattice of 1 are assembled into layers parallel to the bc plane. The Li+ cations and water molecules are located between the layers and the structure is stabilized by hydrogen bonding. The [Fe(thpy)2]- anions form interconnected dimer pairs through hydrogen bonds and short contacts with Fe⋯Fe separation of 6.7861(4) Å. According to dc magnetic measurements, compound 1 demonstrates an incipient spin-crossover transition from the LS (S = 1/2) to the HS (S = 5/2) state above 250 K. The Bleaney-Bowers equation for a model of an isolated LS dimer with a mean-field correction was applied to fit the experimental data of magnetic susceptibility dependence on temperature in the temperature range of 2-250 K. The intra-dimer J1 = -1.79(1) K and inter-dimer J2 = -0.24(3) K antiferromagnetic coupling constants were defined. The analysis of the 57Fe Mössbauer spectra at 80 K and 296 K confirms the presence of the shortened distances between the iron nuclei. Moreover, the influence of the lithium cation on the stabilization of the LS state was shown for the [Fe(thpy)2]- anion. BS-DFT calculations for the optimized structure of two isolated [Fe(thpy)2]- anions also correctly predict a weak exchange J1(calc) = -0.92 K. DFT calculations revealed the OPBE (GGA-type) functional that correctly predicts the spin-crossover transition for the iron(III) thpy compounds. Besides, the effect of the N2O4, N2S2O2, and N2Se2O2 coordination environments on the energy stabilization of the LS state of iron(III) anionic thpy complexes was noted as well.

As a result of the electrochemical oxidation process, the [Fe-III(5Cl-thsa)(2)] spin-crossover (SCO) anion with N2S2O2 coordination sphere transforms into N4O2-coordinated Fe-III SCO neutral binuclear complex 2 with twist of two disulfide bridges. Each dimeric complex is a binuclear double-stranded helicate with similar chirality of both Fe centers. The crystal structure of the complex 2 center dot 3H(2)O at 100 K has a monoclinic C2/c space group and contains large cavities (about 21.5% of the unit cell volume) half-filled by 3 water molecules per one dimer. The N4O2 coordination of iron(III) with two oxygen atoms ( O) of phenoxy groups, two imine-type (-N-im-) nitrogen atoms of azomethine groups, one amidrazone-type (=NamidH) nitrogen atom and one ionized terminal group (-NionizH) of nitrogen has not been observed in CCDC so far. The oxidation state of the iron atoms in the dimeric complex was confirmed by Fe-57 Mossbauer spectroscopy on 90% enriched Fe-57 sample. Mossbauer spectra and dc magnetic measurements demonstrated the partial HS-HS!LS-LS SCO in the 185-225 K temperature range. The details of the structure of complex 2 and the features of its magnetic properties were refined by theoretical analysis based on DFT calculations. The B3LYP* functional correctly predicting the energy of the spin-crossover process was revealed.

Crystals of the new trigonal borate Ва 3 Na 0.9 (OH) 1.9 [B 9 O 16 ][B(OH) 3 ] (sp. gr. P 31 c , a = 10.23684(15) Å, c = 8.72926(13) Å) were prepared by the mild hydrothermal synthesis. The filling of the channels in the framework of the polar nonaborate was found to differ from that determined previously. It is consistent with the main features of this structure type with the preservation of sassoline molecules in the channels. The structure contains an additional ОН group, which is involved in the coordination of Ва.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

New ring silicates Cs 4 Tm 2 [Si 4 O 12 ](OH) 2 and Cs 4 (Tm,Tb) 2 [Si 4 O 12 ](OH) 2 have been synthesized by the hydrothermal method. A structural analogy is revealed between them and the previously studied silicates K 4 Sc 2 (OH) 2 (Si 4 O 12 ) and K 2 Sc[Si 2 O 6 ]F. Their crystal structures are identified as orthorhombic merohedral twins by the lost element of tetragonal symmetry. The structures of new ring silicates are related to those of fresnoite and tetragonal melilite.

Four new cyano-bridged DyIII-CrIII, DyIII-FeIII, HoIII-CrIII and HoIII-FeIII bimetallic coordination polymers were synthesized by the reaction of [Ln(H2dapsc)(H2O)4](NO3)3 (Ln = Dy, Ho); H2dapsc = 2,6-diacetylpyridinebis(semicarbazone)) with K3[M(CN)6] (M = Cr, Fe) in H2O, resulting in the substitution of two water molecules in the coordination sphere of rare earth by paramagnetic tricharged hexacyanides of Fe and Cr. The complexes are isostructural and consist of alternating [Ln(H2dapsc)(H2O)2]3+ and [M(CN)6]3− units linked by bridges of two cis-cyano ligands of the anion to form square-wave chains. The ac magnetic measurements revealed that the DyCr and DyFe complexes are field-induced single molecule magnets, while their Ho analogs do not exhibit slow magnetic relaxation.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Four new heterometallic complexes combining [MII(H2dapsc)]2+ cations with the chelating H2dapsc {2,6-diacetylpyridine-bis(semicarbazone)} Schiff base ligand and [Cr(CN)6]3− anion were synthesized: {[MII(H2dapsc)]CrIII(CN)6K(H2O)2.5(EtOH)0.5}n·1.2n(H2O), M = Mn (1) and Co (2), {[Mn(H2dapsc)]2Cr(CN)6(H2O)2}Cl·H2O (3) and {[Co(H2dapsc)]2Cr(CN)6(H2O)2}Cl·2EtOH·3H2O (4). In all the compounds, M(II) centers are seven-coordinated by N3O2 atoms of H2dapsc in the equatorial plane and N or O atoms of two apical –CN/water ligands. Crystals 1 and 2 are isostructural and contain infinite negatively charged chains of alternating [MII(H2dapsc)]2+ and [CrIII(CN)6]3− units linked by CN-bridges. Compounds 3 and 4 consist of centrosymmetric positively charged trimers in which two [MII(H2dapsc)]2+ cations are bound through one [CrIII(CN)6]3− anion. All structures are regulated by π-stacking of coplanar H2dapsc moieties as well as by an extensive net of hydrogen bonding. Adjacent chains in 1 and 2 interact also by coordination bonds via a pair of K+ ions. The compounds containing MnII (1, 3) and CoII (2, 4) show a significant difference in magnetic properties. The ac magnetic measurements revealed that complexes 1 and 3 behave as a spin glass and a field-induced single-molecule magnet, respectively, while 2 and 4 do not exhibit slow magnetic relaxation in zero and non-zero dc fields. The relationship between magnetic properties and non-covalent interactions in the structures 1–4 was traced.

Mono-deprotonated HIndigo(-) anions have been selectively generated by a direct interaction of H2Indigo with cesium metal in toluene. Following interaction with cryptand allows one to isolate crystalline complex {cryptand (Cs+)}(Cs+)center dot[HIndigo(-)](2)center dot C6H4Cl2 (1). Methods for preparation of chelated complexes of HIndigo(-) with cobalt(II) and nickel(II) halides have also been developed allowing structure and properties of crystalline {CV+}[HIndigo ((CoCl2)-Cl-II)](-)center dot C6H4Cl2 (2) and {cryptand(K+)}[HIndigo((NiCl2)-Cl-II)](-) (3) to be studied. Tetrahedral CoII atoms in 2 have high-spin S = 3/2 state which is evidenced from corresponding EPR spectra and SQUID measurements. Molecular structure and properties of HIndigo- anions have been studied in the obtained complexes and compared with those of mono-reduced H2Indigo(center dot-) radical anions. It is shown that absorption bands of HIndigo(-) are red-shifted relative to those of H2Indigo(center dot-) allowing reduced and deprotonated forms of trans-indigo to be distinguished. HIndigo(-) anions are EPR silent and diamagnetic in contrast to paramagnetic H2Indigo(center dot-) radical anions.

A potassium salt of the N2S2O2-coordination Fe(III) anion K[Fe(5Cl-thsa)2] (1) (5Cl-thsa - 5-chlorosalicylaldehyde thiosemicarbazone) is synthesized and characterized structurally and magnetically over a wide temperature range. Two polymorphs of salt 1 characterized by the common 2D polymer nature and assigned to the same orthorhombic Pbcn space group have been identified. The molecular structure of the minor polymorph of 1 was solved and refined at 100, 250, and 300 K is shown to correspond to the LS configuration. The dominant polymorph of 1 features K+ cations disordered over a few crystallographic sites, while the minor polymorph includes fully ordered K+ cations. The major polymorph exhibits a complete three-step cooperative spin-crossover transition both in the heating and cooling modes: The first step occurs in a temperature range from 2 to 50 K; the second abrupt hysteretic step occurs from 200 to 250 K with T1/2 = 230 K and a 6 K hysteresis loop. The third gradual step occurs from 250 to 440 K. According to 57Fe Mössbauer, XRPD, and EXAFS data, the spin-crossover transition for the dominant polymorph is quite peculiar. Indeed, the increase in the HS concentration by 57% at the second step does not result in the expected significant increase in the iron(III)-ligand bond lengths. In addition, the final step of the spin conversion (ΔγHS = 26%) is associated with a structural phase transition with a symmetry lowering from the orthorhombic (Pbcn) to the monoclinic (P21/n) space group. This nontrivial phenomenon was investigated in detail by applying magnetization measurements, electron spin resonance, 57Fe Mössbauer spectroscopy, and DFT calculations. These results provide a new platform for understanding the multistep spin-crossover character in the Fe(III) thsa-complexes and related compounds.

Metal complexes of trithiadodecaazahexaphyrin (Hhp) that contain MII3O clusters inside a π-extended trianionic (Hhp3-) macrocycle have been prepared. Studies of the magnetic properties of NiII3O(Hhp) and CuII3O(Hhp) reveal a diamagnetic and EPR-silent trianionic (Hhp3-) macrocycle and diamagnetic NiII3(O2-) or paramagnetic CuII3(O2-) tetracations. The positive charge of MII3O(Hhp) is compensated by one acetate anion {MII3O(Hhp)}+(CH3CO2-). The three-electron reduction of {MII3O(Hhp)}+ yields {cryptand(Cs+)}2{NiII2NiIO(Hhp5-)}2-·2C7H8 (1) and {cryptand(Cs+)}2{CuII3O(Hhp•6-)}2-·C7H8 (2) crystalline salts. The magnetic properties of 1 reveal the formation of Hhp5- and the reduction of nickel(II) to the paramagnetic NiI ion (S = 1/2), which is accompanied by the formation of the {NiII2NiIO(Hhp5-)}2- dianion. As a result, the magnetic moment of 1 is 1.68 μB in the 20-220 K range, and a broad EPR signal of NiI was observed. The Hhp5- macrocycle has a singlet ground state, but the increase in the magnitude of the magnetic moment of 1 above 220 K is attributed to the population of the triplet excited state in Hhp5-. The {NiII2NiIO(Hhp5-)}2- dianion is transferred from the doublet excited state to the quartet excited state with an energy gap of 1420 ± 50 K. Salt 1 also shows an unusually strong low-energy NIR absorption, which was observed at 1000-2200 nm. In 2, a highly reduced Hhp•6- radical hexaanion (S = 1/2) coexists with a CuII3(O2-) cluster (S = 1/2) in the {CuII3O(Hhp•6-)}2- dianions. The dianions have a triplet ground state with antiferromagnetic exchange between two S = 1/2 spins with J = -6.4 cm-1. The reduction of Hhp in both salts equalizes the initially alternated C-N bonds, supporting the increase in the Hhp macrocycle electron delocalization.

Reduction of organic dye 3,4:9,10-perylenetetracarboxylic dianhydride (PTCDA) yields a series of radical anion and dianion salts of PTCDA (1-5). Their formation is accompanied by essential red shift and splitting of absorption bands of pristine PTCDA (493 and 560 nm) which appear nearly in the whole visible range, namely, at 660, 700 and 760-770 nm for the radical anions, and 514-526, 544-569, 633-644 and 700-713 nm for the dianions. Weaker bands are also observed in the NIR range at 954 and 938-940 nm, respectively. Reduction elongates double C=O bonds, and the shape of the anions becomes non-planar due to twisting. A dihedral angle between two planar halves of PTCDA increases together with anion charge. The PTCDA(center dot-) radical anions form {PTCDA}(2)(2-) dimers in 1-3 with short interplanar distances of 3.220-3.299 angstrom. These dimers show intense charge transfer bands at 1460-1480 nm and they are diamagnetic up to 360 K indicating large singlet-triplet energy gap for them. The dianions are diamagnetic in the salts. The PTCDA(2- )dianion can also form coordination complexes coordinating two potassium cations in {cryptand(K+)}(2)(PTCDA(2-))center dot C6H4Cl2 (6) or vanadocene cation in {cryptand(K+)}(Cp2V(+))(PTCDA(2-))center dot C6H4Cl2 (7). Mixed {cryptand(K+}(2)(PTCDA(2-)){(GaCl)-Cl-III(Pc center dot 3-)}(center dot-)center dot 2C(6)H(4)Cl(2) (Pc: phthalocyanine, 8) salt containing two strongly absorbing anionic chromophores has also been obtained. Both anions are chequered in the layers forming short C=O(PTCDA Z)center dot center dot center dot H[(GaCl)-Cl-III(Pc center dot 3-)}(center dot-)] hydrogen bonds. Most probably, namely these bonds provide rather effective antiferromagnetic coupling of the [(GaCl)-Cl-III(Pc center dot 3-)}(center dot-)] spins (S = 1/2) within the layers with large negative Weiss temperature of -25 K.