χMT Value Research Articles

Coordination complexes of reduced organic dye isoviolanthrone with transition metals and lanthanides [Mn(II), Dy(III), Gd(III), Nd(III)

The reduction of a vat dye isoviolanthrone to the dianion state in the presence of metal-containing compounds yields binuclear coordination complexes. Two manganese(II) acetylacetonate units coordinate to isoviolanthrone2− (L) in {(K+)cryptand}2{[MnII(acac)2]2⋅L}2– (1) with an average Mn–O bond length of 2.022(2) Å. Dysprosium(III)- or gadolinium(III)-2,2,6,6-tetramethyl-3,5-heptanedionate (TMHD) units form {(K+)cryptand}2{[MIII(TMHD)3]2⋅L}2− (M = DyIII for 2 and GdIII for 3) with the length of the M−O bonds of 2.193(3) and 2.254(4) Å, respectively. Tris(cyclopentadienyl)neodymium(III) forms {(Cs+)cryptand}2{[Cp3NdIII]2⋅L}2–⋅C6H4Cl2 (4) with the Nd–O bonds of 2.264(2) and 2.308(2) Å length. The formation of isoviolanthrone2− is supported by their optical spectra, disappearance of the bands of the CO vibrations in the IR-spectra as well as elongation of the CO bonds in 1–4. High-spin (S = 5/2) MnII atoms in 1 have exchange interaction of J = − 0.122 cm−1 at g = 1.98. Lanthanides have weaker coupling through isoviolanthrone2− in 2 and 3 with J = − 0.029 and D = − 0.004 cm−1 for DyIII and J = 0.0019 cm−1 for GdIII. Complex 4 with two Cp3NdIII species demonstrates the χMT value of 2.33 emu⋅K/mol at 300 K, and this value is lower than the theoretically calculated value of 3.39 emu⋅K/mol. The decrease of χMT is observed in the whole 300–1.9 K range providing negative Weiss temperatures of –32 K. That is explained by magnetic behavior of Cp3NdIII similar to pristine Cp3NdIII. Complexes comprising MnII, GdIII, and NdIII show electron paramagnetic resonance (EPR) signals. Zero-field splitting (ZFS) is observed from MnII and GdIII allowing the estimation of zero-field splitting parameter D as − 0.047 and E close to 0 cm−1 for 1 and − 0.033 and − 0.020 cm−1 for 3. Complex 4 with NdIII manifests an asymmetric two-component EPR signal without ZFS. Weak antiferromagnetic couplings are explained by diamagnetism of isoviolanthrone2− and rather long distances between the metal centers of 15.47–16.25 Å. This study shows that the dianions of organic dyes are promising bidentate ligands for preparation of coordination complexes with d- and f-block metal ions.

Bis(ethylenedithio)tetrathiafulvalene and dibenzotetrathiafulvalene salts with dicyanoiron(III) phthalocyanine anions

Electrooxidation of bis(ethylenedithio)tetrathiafulvelene (BEDT-TTF) and dibenzotetrathiafulvelene (DB-TTF) in the presence of dicyanoiron(II) phthalocyanine (Pc) dianions in form of the {Cryptand(K+)}2{FeII(CN)2Pc}2− salt has been studied in o-dichlorobenzene and acetonitrile solutions (where Cryptand is cryptand[2.2.2]). Initially iron(II) is oxidized to iron(III) and after that tetrathiafulvelenes are oxidized forming crystalline salts (BEDT-TTF+){FeIII(CN)2Pc}−·C6H4Cl2 (1) and (DB-TTF+){FeIII(CN)2Pc}−·C6H4Cl2 (2). Both salts contain closely packed 2D layers composed of the {FeIII(CN)2Pc}− anions and cationic layers containing solvent molecules. Since cations cannot partially oxidize Pc in these salts, two S = 1/2 spins are positioned on FeIII and the cations. The χMT values are 0.90 and 0.87 emu·K/mol per formula unit at 300 K. Antiferromagnetic coupling of spins is observed in 1 and 2 due to both Fe-Cation coupling of −0.4 and −3.5 cm−1 and Fe-Fe couplings of −3.5 and −7.9 cm−1, respectively. Due to its smaller size of DB-TTF+, complex 2 has denser packing of the components and shows stronger exchange couplings. An unusual compound forms when DB-TTF and {FeII(CN)2Pc}2− are oxidized together in acetonitrile: (DB-TTF0)2{Cryptand(K+)}{FeIII(CN)2Pc}− (3) where charges on DB-TTF and Fe are closer to zero and +3, respectively. The {FeIII(CN)2Pc}− anions form layers in 3 among which chains with short C,N…C,N contacts between Pc can be outlined. Only weak intermolecular antiferromagnetic coupling is manifested in 3 with estimated zJ value of −1.6 cm−1.

Halide mediated modulation of magnetic interaction and anisotropy in dimeric Co(II) complexes.

The burgeoning interest in the field of molecular magnetism is to perceive the high magnetic anisotropy in different geometries of metal complexes and hence to draw a magneto-structural correlation. Despite a handful of examples to exemplify the magnetic anisotropy in various coordination geometries of mononuclear complexes, the magnetic anisotropies for two different coordination geometries are underexplored. Employing an appropriate synthetic strategy utilizing the ligand LH2 [2,2'-{(1E,1'E)-pyridine2,6-diyl-bis(methaneylylidine)}-bis(azaneylylidine)diphenol] and cobalt halide salts in a 1 : 2 stoichiometric ratio in the presence of triethylamine allowed us to report a new family of dinuclear cobalt complexes [CoII2X2(L)(P)(Q)]·S with varying terminal halides [X = Cl, P = CH3CN, Q = H2O, S = H2O (1), X = Br, P = CH3CN, Q = H2O, S = H2O (2), X = I, P = CH3CN, and Q = CH3CN (3)]. All these complexes are characterized through single crystal X-ray crystallography, which reveals their crystallization in the monoclinic system P21/n space group with nearly identical structural features. These complexes share vital components, including Co(II) centers, a fully deprotonated ligand [L]2-, halide ions, and solvent molecules. The [L]2- ligand contains two Co(II) centers, where phenolate oxygen atoms bridge the Co(II) centers, forming a Co2O2 four-membered ring. Co1 demonstrates a distorted pentagonal-bipyramidal geometry with axial positions for solvent molecules, while Co2 displays a distorted tetrahedral geometry involving phenolate oxygen atoms and halide ions. Temperature-dependent dc magnetic susceptibility measurements were conducted on 1-3 within a range of 2 to 300 K at 1 kOe. The χmT vs. T plots exhibit similar trends, with χmT values at 300 K higher than the spin-only value, signifying a significant orbital contribution. As the temperature decreases, χmT decreases smoothly in all the complexes; however, no clear saturation at low temperatures is observed. Field-dependent magnetization measurements indicate a rapid increase below 20 kOe, with no hysteresis and a low magnetic blocking temperature. DFT and CASSCF/NEVPT2 theoretical calculations were performed to perceive the magnetic interaction and single-ion anisotropies of Co(II) ions in various ligand-field environments.

Slow magnetic relaxation in a complex of photochromic spiropyran in a merocyanine form and cobalt(II) hexafluoroacetylacetonate.

The interaction between photochromic 8-methoxy-1',3',3'-trimethyl-6-nitro-spiro[chromene-2,2'-indole] (MNSP) and cobalt(II) hexafluoroacetylacetonate yields a deep red-violet solution due to the coordination-induced transition of MNSP from a colorless closed state to a colored open merocyanine (MC) form. The resulting complex {CoII(hfac)2·MNSP} (1) is obtained as crystals, and its structure at 250 K shows the coordination of two oxygen atoms from MNSP with CoII, forming a distorted octahedral surrounding around CoII. The unit cell of 1 contracts below 170 K by 5.5%, which is accompanied by shortening O-Co bonds and altering O-Co-O angles in the structure solved at 150 K. The χMT value of 3.06 emu K mol-1 at 300 K indicates the formation of high-spin CoII (S = 3/2) with a large orbital contribution characteristic of the octahedral surrounding. The contraction of the unit cell of 1 below 170 K provides a reversible 2.2% change of χMT in the 170-160 K range during heating and cooling regimes without hysteresis. The electron paramagnetic resonance signal of 1 was simulated with g-values of gx = 2.342, gy = 2.364, and gz = 2.084, and an isotropic g-factor of 2.267. The temperature-dependent χMT and field-dependent magnetization of 1 allow us to determine a positive zero-field splitting parameter of +20.1 cm-1. A study of the dynamic properties of 1 shows slow magnetic relaxation for CoII in a static field of 1000 Oe. Magnetic hysteresis loops were observed for 1 at 0.5 and 2 K; these loops are closed in the zero field region but opened at fields higher than ±100 and 700 Oe, respectively. The collapse of the loop is observed at 5 K. Excitation of the solution of 1 with green light decreases partially the intensity of the bands of the complex, whereas subsequent exposure of this solution to UV light partially restores these intensities.

A Multiconfigurational Wave Function Theoretical Study on Electronic Structure and Magnetic Susceptibility of Dilanthanide Single Molecule Magnet.

Single molecule magnets (SMMs) have been a promising material for next-generation high-density information storage and molecular spintronics. N23--bridged dilanthanide complexes, {[(Me3Si)2N]2Ln(THF)(μ-η2:η2-N2)(THF)Ln[(Me3Si)2N]2}1-, exhibit high blocking temperatures and have been one of the promising candidates for future application. Rational understanding should be established between the magnetic properties and electronic structure. However, the theoretical study is still challenging due to the complexities in their electronic structures. Here, we theoretically studied the magnetic susceptibility of dilanthanide SMMs based on the state-of-the-art multistate-complete active space self-consistent field and perturbation theory at the second order and restricted active space state interaction with spin-orbit coupling calculations. Temperature dependence of the magnetic susceptibility (χmT-T curve) was quantitatively reproduced by the theoretical calculations. The complexities in the electronic states of these dilanthanide complexes originate from significantly strong static electron correlations in the lanthanide 4f and N2 π* orbitals and the SOC effect. The temperature dependence of the magnetic susceptibility results from the energy levels and magnetic properties of the low-lying excited state. The χmT values below 50 K are dominated by the ground state, while thermal distribution in the low-lying excited state affects the χmT values over 50 K. Saturation magnetization at low temperatures was also evaluated, and the result agrees with the experimental observation.

Structural and Magnetic Analysis of a Family of Structurally Related Iron(III)-Oxo Clusters of Metal Nuclearity Fe8, Fe12Ca4, and Fe12La4

The synthesis, crystal structure, and magnetic characterization are reported for three new structurally related iron(III) compounds (NHEt3)[Fe8O5(OH)5(O2PPh2)10] (1), [Fe12 Ca4O10(O2CPh)10(hmp)4] (2), and [Fe12La4O10(OH)4(tbb)24] (3), where hmpH is 2-(hydroxymethyl)pyridine and tbbH is 4-tBu-benzoic acid. 1 was obtained from the reaction of Fe(NO3)3·9H2O, diphenylphosphinic acid (Ph2PO2H), and NEt3 in a 1:4:16 molar ratio in MeCN at 50 °C; 2 was obtained from the reaction of [Fe3O(O2CPh)6(H2O)3](NO3), Ca(NO3)2, and NEt3 in a 1:1:4:2 ratio at 130 °C; and 3 was obtained from the reaction of Fe(NO3)3·9H2O, La(NO3)3·6H2O, 4-tBu-benzoic acid, and NEt3 in a 1:1:4:4 ratio in PhCN at 140 °C. The core of 1 consists of two {Fe4(µ3-O)2}8+ butterfly units stacked on top of each other and bridged by O2− and HO− ions. The cores of 2 and 3 also contain two stacked butterfly units, plus four additional Fe atoms, two at each end, and four M atoms (M = Ca2+ (2); La3+ (3)) on the sides. Variable-temperature (T) and solid-state dc and ac magnetization (M) data collected in the 1.8–300 K range revealed that 1 has an S = 0 ground state, 2 has a χMT value at low T consistent with the central Fe8 in a local S = 0 ground state and the two Fe3+ ions in each end-pair to be non-interacting, whereas 3 has a χMT value at low T consistent with these end-pairs each being ferromagnetically coupled with S = 5 ground states, plus intermolecular ferromagnetic interactions. These conclusions were reached from complementing the experimental studies with the calculation of the various Fe2 pairwise Jij exchange couplings by DFT computations and by using a magnetostructural correlation (MSC) for polynuclear Fe3+/O complexes, as well as a structural analysis of the intermolecular contacts in the crystal packing of 3.

Structure and Magnetic Properties of Homoleptic Trivalent Tris(alkyl)lanthanides.

Six new solvent-free, homoleptic paramagnetic tris(alkyl)lanthanides Ln{C(SiHMe2)3}3 (1Ln) and Ln{C(SiHMe2)2Ph}3 (2Ln) (Ln = Gd, Dy, and Er) were synthesized to investigate the magnetic properties of 4f organometallic compounds stabilized by secondary Ln↼H-Si and benzylic interactions. The unit cell of 1Gd contains one independent molecule (Z = 2), while 1Dy and 1Er crystallize with four independent isostructural molecules per unit cell (Z = 16). In all molecules, as in other 1Ln compounds, the three tris(dimethylsilyl)methyl ligands form a trigonal planar LnC3 core, and six secondary interactions involving Ln↼H-Si bonding in Ln{C(SiHMe2)3}3 form above and below the equatorial plane. Two and five crystallographically independent molecules of each 2Ln (2Gd, Z = 8; 2Dy, Z = 20) form with three π-coordinated phenyl groups in addition to either one or two secondary Ln↼H-Si interactions per molecule. The packing of these midseries organolanthanide compounds contrasts the single crystallographically unique molecules in previously reported La{C(SiHMe2)3}3 (1La, Z = 2, Z' = 1) and La{C(SiHMe2)2Ph}3 (2La, Z = 2, Z' = 1/3). 2La doped with 2Dy can adopt the crystallographic structure of 2La, which promotes magnetic properties, namely a higher χmT value at low temperatures as well as stronger magnetic anisotropy. The ac susceptibility data for 10% 2Dy doped into 2La suggests slow relaxation at low temperatures with a relaxation barrier of ∼45 K. The computed saturated magnetization of 1Er (M ≈ 4.5 μB) and 1Dy (M ≈ 6 μB) matches the experimental values, while the computed value for 2Dy better matches the value measured for 2Dy diluted in 2La (M ≈ 5 μB). Gas-phase calculations predict that the ground-state and first excited-state multiplet separations are larger for 1Er than 2Er, while the ordering for dysprosium is 1Dy > 2Dy.

Magnetic behavior and ground spin states for coordination {L·[MII(Hal)2]3}3- assemblies (Hal = Cl or I) of radical trianion hexacyanohexaazatriphenylenes (L) with three coordinated high-spin FeII (S = 2) or CoII (S = 3/2) centers.

A series of trianion assemblies of hexaazatriphenylenehexacarbonitrile {HAT(CN)6} and hexaazatrinaphthylenehexacarbonitrile {HATNA(CN)6} with three Fe(II) or Co(II) ions: {cryptand(K+)}3·{HATNA(CN)6·(FeIII2)3}3-·2C6H4Cl2 (1), {cryptand(K+)}3·{HATNA(CN)6·(CoIII2)3}3-·2C6H4Cl2 (2), and (CV+)3·{HAT(CN)6·(CoIICl2)3}3-·0.5(CVCl)·2.5C6H4Cl2 (3) are synthesized (CVCl = crystal violet). Salt 1 has a χMT value of 9.80 emu K mol-1 at 300 K, indicating a contribution of three high-spin FeII (S = 2) and one S = 1/2 of HATNA(CN)6˙3-. The χMT value increases with cooling up to 12.92 emu K mol-1 at 28 K, providing a positive Weiss temperature of +20 K. Such behavior is described using a strong antiferromagnetic coupling between S = 2 and S = 1/2 with J1 = -82.1 cm-1 and a weaker FeII-FeII antiferromagnetic coupling with J2 = -7.0 cm-1. As a result, the spins of three Fe(II) ions (S = 2) align parallel to each other forming a high-spin S = 11/2 system. Density functional theory (DFT) calculations support a high-spin state of CoII (S = 3/2) for 2 and 3. However, the χMT value of 2 and 3 is 2.25 emu K mol-1 at 300 K, which is smaller than 6 emu K mol-1 calculated for the system with three independent S = 3/2 and one S = 1/2 spins. In contrast to 1, the χMT values decrease with cooling to 0.13-0.36 emu K mol-1 at 1.9 K, indicating that spins of cobalt atoms align antiparallel to each other. Data fitting using PHI software for the model consisting of three high-spin Co(II) ions and an S = 1/2 radical ligand shows very large CoII-L˙3- coupling for 2 and 3 with J1 values of -442 and -349 cm-1. The CoII-CoII coupling via the ligand (J2) is also large, being -100 and -84 cm-1, respectively, which is more than 10 times larger than that of 1. One of the reasons for the J2 increase may be the shortening of the Co-N(L) bonds in 3 and 2 to 2.02(2) and 1.993(12) Å. DFT calculations support the population of the quartet state for the Co3 system, whereas the high-spin decet (S = 9/2) state is positioned higher by 680 cm-1 and is not populated at 300 K. This is explained by the large CoII-CoII coupling. Thus, a balance between J1 and J2 couplings provides parallel or antiparallel alignment of the FeII and CoII spins, leading to high- or low-spin ground states of {L·[MII(Hal)2]3}3-.

Modulation of magnetization dynamics of an Er(III) coordination polymer by the conversion of a ligand to a radical using UV light.

Light-induced substance conversion is highly promising for creating new radical-based compounds. Herein, we report an Er(III) coordination polymer [Er(CA)(ACA)(DMF)(H2O)]n (1) and its Y(III)-diluted analogue 1@Y (H2CA = 2,5-dichloro-3,6-dihydroxy-p-quinone, HACA = 9-anthracene carboxylic acid) with the light-induced transformation of the ligand to a radical. The χMT values of light-transformed products 1a and 1a@Y are higher than those of 1 and 1@Y, respectively, due to the formation of radicals by ultraviolet light irradiation, confirmed by EPR measurement as well. The effective energy barriers for magnetization reversal (Ueff) decrease from 72 K for 1 to 67 K for 1a, and from 117 K for 1@Y to 94 K for 1a@Y. This work not only provides a new light-conversion system but also reveals the nature of photo-induced variation of magnetic properties.

Change in the Electronic Structure of the Cobalt(II) Ion in a One-Dimensional Polymer with Flexible Linkers Induced by a Structural Phase Transition

A new 1D-coordination polymer [Co(Piv)2(NH2(CH2)6NH2)]n (1, Piv is Me3CCO2- anion) was obtained, the mononuclear fragments {Co(O2CR)2} within which are linked by μ-bridged molecules of hexamethylenediamine (NH2(CH2)6NH2). For this compound, two different monoclinic C2/c (α-1) and P2/n (β-1) phases were found at room temperature by single-crystal X-ray diffraction analysis, with a similar structure of chains and their packages in unit cells. The low-temperature phase (γ-1) of crystal 1 at 150 K corresponds to the triclinic space group P-1. As the temperature decreases, the structural phase transition (SPT) in the α-1 and β-1 crystals is accompanied by an increase in the crystal packing density caused by the rearrangements of both H-bonds and the nearest ligand environment of the cobalt atom ("octahedral CoN2O4 around the metal center at room temperature" → "pseudo-tetrahedral CoN2O2 at 150 K"). The SPT was confirmed by DSC in the temperature range 210-150 K; when heated above 220 K, anomalies in the behavior of the heat flow are observed, which may be associated with the reversibility of SPT; endo effects are observed up to 300 K. The SPT starts below 200 K. At 100 K, a mixture of phases was found in sample 1: 27% α-1 phase, 61% γ-1 phase. In addition, at 100 K, 12% of the new δ-1 phase was detected, which was identified from the diffraction pattern at 260 K upon subsequent heating: the a,b,c-parameters and unit cell volume are close to the structure parameters of γ-1, and the values of the α,β,γ-angles are significantly different. Further heating leads to a phase transition from δ-1 to α-1, which both coexist at room temperature. According to the DC magnetometry data, during cooling and heating, the χMT(T) curves for 1 form a hysteresis loop with ~110 K, in which the difference in the χMT values reaches 9%. Ab initio calculations of the electronic structure of cobalt(II) in α-1 and γ-1 have been performed. Based on the EPR data at 10 K and the ab initio calculations, the behavior of the χMT(T) curve for 1 was simulated in the temperature range of 2-150 K. It was found that 1 exhibits slow magnetic relaxation in a field of 1000 Oe.

π-Pimer, π-Dimer, π-Trimer, and 1D π-Stacks in a Series of Benzene Triimide Radical Anions: Substituent-Modulated π Interactions and Physical Properties in Crystalline State

π-Pimer, π-Dimer, π-Trimer, and 1D π-Stacks in a Series of Benzene Triimide Radical Anions: Substituent-Modulated π Interactions and Physical Properties in Crystalline State

A Smart Molecule Showing Spin Crossover Responsive Aggregation-Induced Emission

A Smart Molecule Showing Spin Crossover Responsive Aggregation-Induced Emission

Slow Phase Transition-Induced Scan Rate Dependence of Spin Crossover in a Two-Dimensional Supramolecular Fe(III) Complex

Slow Phase Transition-Induced Scan Rate Dependence of Spin Crossover in a Two-Dimensional Supramolecular Fe(III) Complex

Air-Stable Dy(III)-Macrocycle Enantiomers: From Chiral to Polar Space Group

Air-Stable Dy(III)-Macrocycle Enantiomers: From Chiral to Polar Space Group

A Cu(II) Metal Organic Framework with a Tetranuclear Core: Structure, Magnetism, and Supercapacitor Activity

A Cu(II) coordinated metal–organic framework, {[Cu4(BTC)2(4-APy)2(μ3-OH)2]·[(CH3OH)0.5]2·(H2O)2}n (Cu-MOF), has been synthesized by the solvo-diffusion of Cu(NO3)2 to an alcoholic solution of 4-aminopyridine (4-APy) and 1,3,5-benzenetricarboxylic acid (H3BTC) in equimolar proportion. A single-crystal X-ray structure determination suggests that the four-Cu(II)-connected motif ([CuII]4) via edge sharing of two Cu3–O cores and bridging by six acetato functions of the BTC3– connector generates two five-coordinated distorted-square-pyramidal CuO5 units and two distorted-square-planar CuO4 units; the Cu(II) knot in the latter one (CuO4) is coordinated by pyridyl-N of 4-APy. The remaining donor centers of acetato-O of BTC3– bind adjacent [CuII]4 core to form an infinite 3D network structure. The coordination of CH3OH and H2O forms different hydrogen bonds to make a strong superstructure. A surface morphology determination shows a nanoflower pattern. The hybrid material Cu-MOF exhibits a very high specific capacitance, 547 F g–1, at a scan rate of 2 mV s–1 with excellent recycling stability (retains 97.4% after 5000 cycles). The χMT value for Cu-MOF at 300 K is 1.735 cm3 mol–1 K for four copper(II) ions, which is as expected for four isolated copper(II) ions with g = 2.15. The χMT values are almost constant until ca. 55 K, and then χMT decreases sharply, giving a minimum value of 0.753 cm3 K mol–1 at 2 K.

Synthesis, optical and magnetic research of nicotinic acid ligand Zn, Cd, Mn and Co complexes

In this study, a multiple binding sites ligand, 5-(4-carboxyphenoxy)nicotinic acid ligand (H2cpna), was used to construct metal complexes with Zn2+, Cd2+, Mn2+ and Co2+ by solvothermal reaction, and four new complexes were constructed, namely, [Zn (cpna)•H2O]n (1)，[Cd (cpna) (CH3CN)·2H2O]n (2), [Mn (cpna)•2H2O]n (3) and Co(cpna)•2H2O]n (4); All the complexes were characterized by single crystal X-ray diffraction, elemental analysis and infrared analysis in the solid state; Single crystal x-ray diffraction analyses reveal that complexes 1 and 2 have two-dimensional network structures, complexes 3 and 4 have three-dimensional structures. In addition, Luminescence behavior of complex 1 and 2 was investigated and magnetic properties of complex 3 and 4 were studied. The fluorescent test results show that the fluorescence intensity of complex 1 is higher than that of ligand and emission band can be considered as LLCT emission of ligand; The Magnetic results indicate weak ferromagentic interactions in complex 3 and χmT value rises slowly and then decreases sharply from 300 ​K to 2 ​K. However, magnetic results indicate antiferromagentic interactions in complex 4 and χmT value can be divided into three parts with the change of temperature from 300 ​K to 2 ​K.

Synthesis, structures, characterizations and catalytic behaviors for hydrogen evolution of copper(II) and copper(I) complexes supported by diiminodiphosphines

Reactions of N,N’-bis[o-(diphenylphosphino)benzylidene]ethylenediamine (en-P2) with Cu(ClO4)2 or CuClO4 afford two complexes, [CuII-en-P2(NCMe)](ClO4)21 and [CuI-en-P2]ClO42, respectively, which have been characterized by several physico-chemical and spectroscopic methods. The copper atom is five, and four-coordinated in the copper complexes 1 and 2, respectively. At room temperature, en-P2 shows photoluminescence at 420 and 560 nm, however, the addition of Cu2+ or Cu+ leads to a decrease on the peak intensities at 420 and 560 nm, respectively. Investigations for magnetic behaviors show that upon cooling from 300 to 2 K, the χMT value of both copper complexes 1 and 2 steadily increased. Additionally, electrochemical investigations reveal that both complexes 1 and 2 have electrocatalytic activity for hydrogen evolution from acetic acid or water, and complex 1 shows a more efficient activity than complex 2.

Copper(II) and Copper(I) Complexes Supported by Diiminodiphosphines from a Pot Reaction Under Air

A pot reaction of N,N’-bis[o-(diphenylphosphino)benzylidene]ethylenediamine (en-P2) and Cu(ClO4)2 affords two copper complexes with different oxidation sates, [CuII-en-P2(NCMe)](ClO4)21 and [CuI-en-P2]ClO42+ or Cu+ leads to a decrease on the peak intensities at 420 and 560 nm, respectively. Investigations for magnetic behaviors show that upon cooling from 300 to 2 K, the χMT value of both copper complexes 1 and 2 steadily increased. Additionally, electrochemical investigations reveal that both complexes 1 and 2 have electrocatalytic activity for hydrogen evolution from acetic acid or water, and complex 1 shows a more efficient activity than complex 2. The findings show that transition metal complexes may exhibit various functions in different directions.

Tuning Magnetic Relaxation in Square-Pyramidal Dysprosium Single-Molecule Magnets Using Apical Alkoxide Ligands

Tuning Magnetic Relaxation in Square-Pyramidal Dysprosium Single-Molecule Magnets Using Apical Alkoxide Ligands

Magnetic Exchange through the Dianionic Hexaazatrinaphthylene (HATNA) Ligand in {HATNA(FeIICl2)3}2− Containing FeII (S=2) Triangles

AbstractHerein, a new method for the preparation of anionic hexaazatrinaphthylene (HATNA) coordination complexes was developed. The reduced HATNA coordinated three FeIICl2 units for the formation of (CV+)2{HATNA(FeIICl2)3}2− ⋅ 3.5 C6H4Cl2 (1) (CV+ is a cationic form of crystal violet). The FeII atoms had a high S=2 spin state and were arranged in nearly equilateral triangles at a distance of approximately 7 Å. The χMT value of 1 was 9.70 emu⋅K/mol at 300 K, exceeding the calculated spin‐only value of three independent high‐spin FeII centers (S=2) (9.00 emu⋅K/mol). A strong antiferromagnetic exchange was observed between FeII atoms through the diamagnetic HATNA units since Weiss temperature is −98 K. Magnetic behavior of 1 was modelled by PHI package obtaining the exchange interaction constant J=−4.6 cm−1 and zero‐field splitting parameter D=5.6 cm−1 at g=2.23. Arrangement of magnetic centers in the equilateral triangles supposes that some degree of spin frustration exists in 1. Crystal structures of two phases of pristine HATNA molecule are also reported.