Two new ion-pair complexes containing derivatives of substituted benzyl isoquinolinium and bis(maleonitriledithiolato)nickelate monoanion: 3D crystal structures, magnetic properties and theoretical analyses

Syntheses, structural characterizations, magnetic behaviors and theoretical analyses of two new ion-pair complexes, [IFBzIQl][Ni(mnt)₂](1) and [IClBzIQl]₂[Ni(mnt)₂]₂ · MeCN(2) [IFBzIQl][Ni(mnt)₂] ([IFBzIQl]⁺ = 1-(2′-fluoro-4′-iodobenzyl)isoquinolinium, [IClBzIQl]⁺ = 1-(2′-chloro-4′-iodobenzyl)isoquinolinium, mnt²⁻ = maleonitriledithiolate), have been investigated. In crystal of 1, the [Ni(mnt)₂]⁻ anions and the [IFBzIQl]⁺ cations stack into an alternating column through π?π stacking interactions. The anions of both 1 and 2 form a dimer via π?π stacking and S?S short interactions between the [Ni(mnt)₂]⁻ anions. The overlapping mode of two neighboring [Ni(mnt)₂]⁻ anions in the dimer is the Ni-ring fashion with a Ni?Ni distance of 4.076 Å for 1, and ring-ring fashion with the Ni?Ni and S?S distances being 4.395 and 3.593 Å for 2. Some weak interactions such as π?π, C?N, C-H?F or C-H?N in 1 and 2 play a crucial role in stacking and stabilizing the crystal lattice, and give a 3D network structure and exchange pathways of the magnetic interaction for 1 and 2. Magnetic susceptibility measurements for 1 and 2 in the temperature range 1.8-300 K show that the overall magnetic behavior indicates the presence of antiferromagnetic interaction, while 2 exhibits an activated magnetic behavior in the high-temperature region (HT) together with a Curie tail in the low-temperature region (LT).     

2D crystal structure, magnetic behavior and theoretic analysis of two new molecular solids based on Ni(maleonitriledithiolate)2 monoanion with substituted 2-aminopyridinium

Two new molecular solids, [BzPyNH₂][Ni(mnt)₂](1) and [2-NpCH₂PyNH₂][Ni(mnt)₂](2) (mnt²⁻ = maleonitriledithiolate, [BzPyNH₂]⁺ = 1-benzyl-2-aminopyridinium and [2-NpCH₂PyNH₂]⁺ = 1-(2′-naphthylmethylene)-2-aminopyridinium) have been characterized structurally and magnetically. The Ni(Ш) ions of 1 and 2 form a 1D magnetic chain within a [Ni(mnt)₂]⁻ column through Ni?N or π?π interactions. Some weak interactions observed in 1 and 2 give further rise to a 2D structure. The overlapping fashions of the [Ni(mnt)₂]⁻ anions are different when the 2-aminopyridine ring was fixed and the phenyl ring changed into the naphthyl ring of the cation. Magnetic susceptibility measurements in the temperature range 2-300 K show that 1 is weak antiferromagnetic coupling, while 2 exhibits a novel and interesting spin-gap transition around 140 K with Δ/k_b = 381.4 K.     

Syntheses, crystal structures, and magnetic properties of two novel Ni(mnt)2-based molecular magnetic materials containing substituted triphenylphosphinium

Two novel molecular magnetic materials, [RBzTPP][Ni(mnt)₂] (mnt²⁻ = maleonitriledithiolate, [RBzTPP]⁺ = 4-R-benzyltriphenylphosphinium; R = CN (1), Cl (2)) were synthesized and characterized by X-ray diffraction, IR spectroscopy, and magnetic susceptibility measurements. In crystal of 1, the [Ni(mnt)₂]⁻ anions form a dimer via Ni?S and π?π stacking interactions between Ni(mnt)₂ planes, and the C-H?Ni and C-H?N H-bonding interactions are found between the [Ni(mnt)₂]⁻ anions and the neighboring [CNBzTPP]⁺ cations. The anions and cations of 2 stack into well-segregated columns in the solid state; and the Ni(III) ions form a 1D alternating chain in a Ni(mnt)₂ column through intermolecular Ni?S, or π?π interactions with the Ni?Ni distances of 3.900, 4.198, and 4.165 Å. Magnetic susceptibility measurements for these complexes in the temperature range 1.8-300 K show that the overall magnetic behavior for 1 and 2 indicates the presence of antiferromagnetic interaction, but 1 exhibits an activated magnetic behavior in the high-temperature (HT) region together with a Curie tail in the low-temperature (LT) region.     

Two salts containing bis(maleonitriledithiolate)nickel(III)/copper(II) anion and substituted benzyltriphenylphosphinium: Syntheses, crystal structures and magnetic properties

Syntheses, crystal structures and magnetic properties of two salts, [FBzTPP][Ni(mnt)₂](1) and [FBzTPP]₂[Cu(mnt)₂](2) ([FBzTPP]⁺ = 1-(4′-fluorobenzyl)triphenylphosphinium, mnt²⁻ = maleonitriledithiolate), are investigated. In 1, the anions and cations stack into well-segregated columns, and the Ni(III) ions form a 1D alternating chain in a [Ni(mnt)₂]⁻ column through intermolecular Ni?S and π?π interactions with the Ni?Ni distances of 3.939, 4.057 and 4.101 Å, and the C-H?N hydrogen bonds are found between the [Ni(mnt)₂]⁻ anion and the neighboring [FBzTPP]⁺ cation. The [Cu(mnt)₂]²⁻ anions in 2 do not form a column and no weak interactions exist between the anions duo to isolation of the [FBzTPP]⁺ cations, while C-H?F and C-H?S hydrogen bonds were found in 2. Magnetic susceptibility measurements in the temperature range 2-300 K show that 1 exhibits a spin-gap transition around 46 K, and antiferromagnetic interaction (θ = −49.0 K) in the high-temperature phase (HT) and spin gap (Δ/k_b = 88.2 K) in the low-temperature phase (LT), while 2 shows a very weak antiferromagnetic coupling behavior with θ = −1.33 × 10⁻² K.     

Synthesis, crystal structure and magnetic characterization of two new ion-pair complexes containing bis(maleonitriledithiolate)nickelate anion and substituted benzylpyridinium cation

Two new ion-pair complexes, [FBrBzPyN(CH₃)₂]₂[Ni(mnt)₂] (1) and [FBrBzPyN(CH₃)₂][Ni(mnt)₂] (2) (mnt²⁻ = maleonitriledithiolate, [FBrBzPyN(CH₃)₂]⁺ = [1-(4′-fluoro-2′-bromobenzyl)-4-dimethylaminopyridinium]) have been prepared and characterized by elemental analyses, UV, IR, single crystal X-ray diffraction and magnetic susceptibility. The cations (D) and the anions (A) in 1 stack into a 1D alternating column (i.e., of type ?DDADDADD?) via short S?Br, N?F, C?N interactions, and C-H?Br hydrogen bonds. The cation-cation π?π stacking interactions within the columns give further rise to a 2D network structure. Compound 2 forms a 3D structure in which the Ni(III) ions stack into a uniform 1D zigzag magnetic chain through Ni?S, Ni?Ni, or π?π interactions with a Ni?Ni distance of 4.024 Å. Magnetic susceptibility measurements in the temperature range 2-300 K show that 1 is expected to be diamagnetic, and 2 exhibits an interesting spin-gap transition (Δ/k_b = 460.6 K) around 155 K.     

Syntheses, crystal structures, and magnetic properties of Ni(mnt)2-based molecular solids containing substituted isoquinolinium

Two novel ion-pair complexes, [RBzIQl]⁺[Ni(mnt)₂]⁻ (mnt²⁻ = maleonitriledithiolate, [RBzIQl]⁺ = 4-R-benzylisoquinolinium; R = H (1), Cl (2)) have been characterized structurally and magnetically. The anions and [BzIQl]⁺ cations of 1 form 1D column of alternating between cations and anions via π?π stacking interaction between Ni(mnt)₂ plane and isoquinoline ring, and the Ni(mnt)₂ anions between adjacent columns exist C?N, C?N, and N?N interaction. The anions and cations of 2 stack into well-segregated columns in the solid state; and the Ni(III) ions form a 1D zigzag chain in a Ni(mnt)₂ column through intermolecular Ni?S, S?S, Ni?Ni or π?π interactions. The chain is uniform in 2 with the Ni?Ni distances of 3.784 Å. Magnetic susceptibility measurements for these complexes in the temperature range 1.8-300 K show that 1 exhibits antiferromagnetic coupling behavior, and 2 exhibits unusual magnetic phase transitions around 45 K. The overall magnetic behavior for 2 indicates the presence of antiferromagnetic interaction in the high-temperature phase (HT) and spin gap in the low-temperature phase (LT).     

Syntheses, structures, and magnetic properties of two new molecular magnets containing Ni(mnt)2 monoanion and substituted 4-dimethylaminopyridinium

Two new molecular magnets, [BzPyN(CH₃)₂][Ni(mnt)₂] (1) and [NO₂BzPyN(CH₃)₂][Ni(mnt)₂] (2)([BzPyN(CH₃)₂]⁺ = 1-benzyl-4-dimethylaminopyridinium, [NO₂BzPyN(CH₃)₂]⁺ = 1-(4′-nitrobenzyl)-4-dimethylaminopyridinium, and mnt²⁻ = maleonitriledithiolate) have been prepared and characterized by elemental analyses, IR, MS spectra, single crystal X-ray diffraction and magnetic susceptibility. The Ni(III) ions of both 1 and 2 form a 1D zigzag alternating magnetic chain within a column through Ni?S, Ni?Ni, Ni?N, S?S, or π?π interactions. Magnetic susceptibility measurements in the temperature range 1.8-300 K show that 1 exhibits antiferromagnetic behavior, while 2 shows a spin gap transition around 170 K, and antiferromagnetic interaction in the high-temperature phase (HT) and spin gap in the low-temperature phase (LT). The phase transition for 2 is second-order by determination of DSC analyses.     

Use of a cubane-type Mo3CoS4 molecular cluster as paramagnetic unit in the synthesis of hybrid charge-transfer salts

Selective substitution of the chlorine atom coordinated to cobalt in the paramagnetic Mo₃(CoCl)S₄(dmpe)₃Cl₃ (dmpe = 1,2-bis(dimethylphosphanyl) ethane) complex with a S = 1/2 ground state has been achieved by iodine oxidation to afford the also paramagnetic [Mo₃(CoI)S₄(dmpe)₃Cl₃]I ([1]I) salt with a S = 1 ground state in almost quantitative yield. Replacement of chorine by iodine has no significant effect on the structural and electrochemical properties of the Mo₃CoS₄ system. Metathesis of the [1]I salt with the paramagnetic nickel anionic dithiolate [Ni(mnt)₂]⁻ (mnt = maleonitrilodithiolate) affords [1]₂[Ni(mnt)₂]. The stoichiometry evidenced by X-ray analysis reveals that reduction of the [Ni(mnt)₂]⁻ radical to the corresponding diamagnetic closed shell [Ni(mnt)₂]²⁻ dianion, presumably via dismutation, has occurred during the metathesis process. The crystal structure of [1]₂[Ni(mnt)₂] consists of [Ni(mnt)₂]²⁻ dianions sandwiched by two cluster 1⁺ cations which yield {1⁺·[Ni(mnt)₂]²⁻·1⁺} subunits arranged along the crystallographic c axis. Magnetic susceptibility measurements for [1]₂[Ni(mnt)₂] show a χT product of 0.99 emu K/mol largely unchanged in the 10-300 K range. This behavior agrees with the presence of an S = 1 cluster 1⁺ cation while the Ni(mnt)₂ moiety does not contribute to the paramagnetism of the sample.     

Syntheses, crystal structures, and magnetic properties of two new 1D molecular solids based on Ni(mnt)2 ion

Two novel ion-pair complexes, 1-(4′-bromo-2′-fluorobenzyl)isoquinolinium-bis(maleonitrile dithiolato)nickel(III), [BrFBzIQl] · Ni(mnt)₂ · 0.5MeCN (1) and 1-(4′-bromo-2′-flourobenzyl)-quinolinium-bis(maleonitriledithiolato)nickel(III), [BrFBzQl] · Ni(mnt)₂ (2) have been characterized structurally and magnetically. The anions and cations of 1 stack into columns in the solid state, respectively; and the Ni(III) ions form uniform stacking column with the Ni?Ni distances 4.061 Å within a column through intermolecular Ni?S, S?S, Ni?Ni or π?π interactions, while 2 forms 1D column of alternating between cations and anions via the hydrogen bonds, C?N, C?N, N?C, and π?π interactions. The changes of coupling constants were observed in these two complexes at 85 K for 1 and 70 K for 2. It is interesting that 1 undergoes a transition from antiferromagnetic to ferromagnetic phase and 2 does counter to that of 1.     

Syntheses, structures and magnetic properties of three new ion-pair complexes containing transition metal bis(malconitriledithiolate) anion and radical cations

Three new ion-pair complexes (m-MPYNN)₂Ni(mnt)₂ (1), (p-MPYNN)₂Ni(mnt)₂ (2) and (p-MPYNN)₂Cu(mnt)₂ (3) (m- or p-MPYNNI = [3- or4- (4,4,5,5-tetramethyl-1-oxido-3-oxyl-4,5-dihydro-3H-imidazol-2′-yl)-1-methylpyridinium] iodide, mnt = maleonitriledithiolate) have been prepared and characterized by elemental analyses, IR, single crystal X-ray diffraction and magnetic susceptibility. In complex 1, the m-MPYNN cations form a centrosymmetric dimer, and the [Ni(mnt)₂]²⁻ anion lies on a center of inversion. Complexes 2 and 3 show layered packing, and the p-MPYNN cations lie between the layers of the anions. Magnetic susceptibility measurements in the temperature range 2-300 K show that the three complexes exhibit weak antiferromagnetic behaviors. The behavior of complex 1 was explained with the singlet-triplet model.     

Synthesis and electrochemical studies of octahedral nickel β-diketonate complexes

The reaction of [Ni(tmhd)₂] and [Ni(dbm)₂] with N-donor chelating ligands in dichloromethane and acetone, respectively, yields the complexes [Ni(tmhd)₂(L-L)] (L-L = 2,2′-bpy 1, phen 2 and dmae 3) and [Ni(dbm)₂(L-L)] (L-L = 2,2′-bpy 4, phen 5, dmae 6). UV-Vis spectroscopy shows very strong bands in the UV region consistent with ligand centred π → π^∗ transitions. The electrochemical studies of 1-6 reveal oxidation to Ni(III). The [Ni(tmhd)₂(L-L)] 1-3 are more easily oxidized by ca. 300 mV and are quasi-reversible whereas for the [Ni(dbm)₂(L-L)] series only complex 6 shows significant reversibility. X-ray crystallographic studies have been conducted in the case of [Ni(dbm)₂(phen)] 5 and [Ni(dbm)₂(dmae)] 6. The structures both show that the nickel metal centre is octahedral with an O₄N₂ coordination environment. In the structures the β-diketonate ligands exhibit a cis-arrangement, with the metal displaced out of the planar chelate ring.     

Three ion-pair complexes containing bis(maleonitriledithiolate)copper(II) anion and substituted 4-dimethylaminopyridinium: Syntheses, crystal structures, and magnetic properties

Three new ion-pair complexes, [4RBzDMAP]₂[Cu(mnt)₂] (mnt²⁻ = maleonitriledithiolate; [4RBzDMAP]⁺ = 1-(4′-R-benzyl)-4-dimethylaminopyridinium, R = F(1), Cl(2) and Br(3)) were synthesized and characterized by elemental analyses, IR, UV, single crystal X-ray diffraction and magnetic measurements. The [Cu(mnt)₂]²⁻ anions and the cations stack alternately and form a 1D column via C-H···S, C-H···π or C-H···Cu interactions for 1 and 2. While the cations stack into a column though π···π or C-H···π interactions between pyridine and phenyl rings for 1 and 3. The change of the molecular topology of the counteraction when the 4-substituted group in the benzyl ring have been changed from F or Cl to Br atom, results in the difference in the crystal system, space group and the stacking mode of the cations and anions of 1, 2 and 3. Some weak hydrogen bonds between the adjacent columns further generate a 3D network structure. It is interesting that 1 and 2 exhibits antiferromagnetic coupling with θ = −2.372 K and θ = −14.732 K, while 3 shows weak ferromagnetic coupling feature with θ = 0.381 K.     

Stereosensitive formation and interconversion of sulfur-bridged cobalt(III)-mercury(II) polynuclear complexes with d- and/or l-penicillaminates

The reaction of trans(N)-[Co(d-pen)₂]⁻ (pen = penicillaminate) with HgCl₂ or HgBr₂ in the molar ratios of 1:1 gave the sulfur-bridged heterodinuclear complex, [HgX(OH₂){Co(d-pen)₂}] (X = Cl (1a) or Br (1b)). A similar reaction in the ratio of 2:1 produced the trinuclear complex, [Hg{Co(d-pen)₂}₂] (1c). The enantiomers of 1a and 1c, [HgCl(OH₂){Co(l-pen)₂}] (1a′) and [Hg{Co(l-pen)₂}₂] (1c′), were also obtained by using trans(N)-[Co(l-pen)₂]⁻ instead of trans(N)-[Co(d-pen)₂]⁻. Further, the reaction of cis · cis · cis-[Co(d-pen)(l-pen)]⁻ with HgCl₂ in the molar ratio of 1:1 resulted in the formation of [HgCl(OH₂){Co(d-pen)(l-pen)}] (2a). During the formations of the above six complexes, 1a, 1b, 1c, 1a′, 1c′, and 2a, the octahedral Co(III) units retain their configurations. On the other hand, the reaction of cis · cis · cis-[Co(d-pen)(l-pen)]⁻ with HgCl₂ in the molar ratio of 2:1 gave not [Hg{Co(d-pen)(l-pen}₂] but [Hg{Co(d-pen)₂}{Co(l-pen)₂}] (2c), accompanied by the ligand-exchange on the terminal Co(III) units. The X-ray crystal structural analyses show that the central Hg(II) atom in 1c takes a considerably distorted tetrahedral geometry, whereas that in 2c is of an ideal tetrahedron. The interconversion between the complexes is also examined. The electronic absorption, CD, and NMR spectral behavior of the complexes is discussed in relation to the crystal structures of 1c and 2c.     

Cd(II)-NCS/NCO complexes of 1-alkyl-2-(arylazo)imidazole: Single crystal X-ray structure of [Cd(HaaiMe)2(SCN)2]

The reaction of Cd(OAc)₂ · 4H₂O and 1-alkyl-2-(arylazo)imidazole [RaaiR′ where R = H (a), Me (b); R′ = Me (1/3/5), Et (2/4/6)] and NH₄NCS/NaNCO in methanol in 1:2:2 mole ratio has afforded [Cd(RaaiR′)₂(NCS)₂] (3, 4) and [Cd(RaaiR′)₂(NCO)₂] (5, 6) complexes. The complexes are characterized by different physicochemical methods and in one case, the structure was confirmed by single crystal X-ray diffraction study for title compounds.     

β-Diiminatolanthanoid(III) halides revisited

The crystalline compounds [LnCl₂(L)(thf)₂] [Ln = Ce (1), Tb (2), Yb (3)], [NdI₂(L)(thf)₂] (4), [LnCl(L′)₂] [Ln = Tb (5), Yb (6) (a known compound)] and [YbCl(L′′)(μ-Cl)₂Li(OEt₂)₂] (7) have been prepared [L = {N(C₆H₃Prⁱ₂-2,6)C(H)}₂CPh, L′ = {N(SiMe₃)C(Ph)}₂CH, L′′ = {N(SiMe₃)C(C₆H₄Ph-4)}₂CH]. The X-ray molecular structures of 2-7 have been established; in each, the monoanionic ligand L, L′ or L′′ is N,N′-chelating and essentially π-delocalised. Each of 1-7 was prepared from the appropriate LnCl₃, or for 4 [NdI₃(thf)₂], and an equivalent portion of the appropriate alkali metal [Li for 7, Na for 2, 3 and 5, or K for 1, 4 and 6] β-diiminate in thf; the isolation of exclusively 5 and 6 (rather than the L′ analogues of 2 or 3) is noteworthy, as is the structure of 7 which has no precedent in Group 3 or 4f metal β-diiminato chemistry.     

Synthesis, structure and electronic spectra of new three-coordinated copper(I) complexes with tricyclohexylphosphine and diimine ligands

Three new copper(I) complexes with tricyclohexylphosphine (PCy₃) and different diimine ligands, [Cu(phen)(PCy₃)]BF₄ (1) (phen = 1,10′-phennanthroline), [Cu(bpy)(PCy₃)₂]BF₄ (2) (bpy = 2,2′-bipyridine) and [Cu(MeO-CNN)(PCy₃)]BF₄ (3) (MeO-CNN = 6-(4-methoxyl)phenyl-2,2′-bipyridine), have been synthesized and characterized. X-ray structure reveals that complexes 1 and 3 are three-coordinated with trigonal geometry, while complex 2 adopts distorted tetrahedron geometry. Complexes 1 and 3 exhibit ligand redistribution reactions in chloromethane solution by addition of excess amount of PCy₃, in which three-coordinated 1 changes into four-coordinated [Cu(phen)(PCy₃)₂]⁺, and 3 leads to form [Cu(PCy₃)₂]BF₄ and CNN-OMe. All the three complexes display yellow ³MLCT emissions in solid state at room temperature with λ_max at 558, 564 and 582 nm for 1, 2 and 3, respectively, and red-shift to 605, 628 and 643 nm at 77 K in dichloromethane solution.     

Synthesis, spectroscopic, thermal and X-ray structure characterization of 1,3-propanediammonium tetrathiomolybdate and N,N,N′,N′-tetramethylethylenediammonium tetrathiomolybdate

The title compounds 1,3-propanediammonium tetrathiomolybdate, (1,3-pnH₂)[MoS₄], 1 and, N,N,N′,N′-tetramethylethylenediammonium tetrathiomolybdate, (tmenH₂)[MoS₄], 2, were prepared by reacting the ammonium salt of [MoS₄]²⁻ with the corresponding organic diamine. In 1 and 2 the organic diamines 1,3-propanediamine (1,3-pn) and N,N,N′,N′-tetramethylethylenediamine (tmen) are present in their diprotonated form. The reaction of 1 or 2 with [Ni(en)₃]Cl₂ · 2H₂O (en is ethylenediamine) results in the formation of the highly insoluble complex tris(ethylenediamine)Ni(II) tetrathiomolybdate, [Ni(en)₃][MoS₄], in quantitative yields. 1 and 2 have been characterized by chemical analysis, vibrational, UV-Vis and NMR spectroscopy, TG-DTA-MS and single crystal X-ray crystallography. Compound 1 is thermally more stable compared to 2. Both complexes decompose in a single step forming amorphous molybdenum sulfide. The structure of the title complexes can be described as consisting of tetrahedral [MoS₄]²⁻ dianions which accept a complex series of H-bonds from the organic dications. The strength and number of these hydrogen bonds affect the Mo-S bond lengths.     

Pseudohalide-bridged five-coordinate Ni(II) or Co(II) complexes with bulky bidentate ligands: Magneto-structural correlationship

Bidentate ligands 2,2′-biquinoline (biq) and 6,6′-dimethyl-2,2′-bipyridine (dmbpy) with steric hindrance substituents cis to the nitrogen atoms have been used in the synthesis of transition metal complexes. Six new doubly end-on azido-bridged binuclear complexes [M₂(biq)₂(μ_1,1-N₃)₂(N₃)₂] (M = Ni (1), M = Co (2)), [M₂(biq)₂(μ_1,1-N₃)₂Cl₂] (M = Ni (3), M = Co (4)), [M₂(dmbpy)₂(μ_1,1-N₃)₂(N₃)₂] (M = Ni (5), M = Co (6)) and one end-to-end thiocyanato-bridged polymeric [Ni(dmbpy)(μ_1,3-SCN)(NCS)]_n (7) have been synthesized and characterized by single crystal X-ray diffraction analysis and magnetic studies. Complexes 1-6 comprise five-coordinate M(II) ions bridged by two end-on azide ligands. The bridging M-N-M bond angles are in the small range 104.1-105.2°. Complex 7 consists of a singly thiocyanate-bridged Ni(II) chain in which Ni(II) ions are five-coordinate. This research suggests that the bulky ligands play a key role in the formation of five-coordinate coordination structure. All complexes display intramolecular intermetallic ferromagnetic coupling with J_NiNi and J_CoCo of ca. 23 or 13 cm⁻¹ based on the Hamiltonian (S₁ = S₂ = 1 for Ni₂, or 3/2 for Co₂). The singly SCN⁻-bridged chainlike complex 7 shows intrachain ferromagnetic interaction with J = 3.96(2) cm⁻¹ and D = −4.55(8) cm⁻¹ (. Magneto-structural correlationship has been investigated.     

Mixed-ligand tris chelated complexes of Mo(IV) and W(IV): A comparative study

Two hitherto unknown mixed-ligand tris chelated complexes containing 2-aminothiophenolate, [Et₄N]₂[M^IV(NH-(C₆H₄)-S)(mnt)₂] (M = Mo, 1a; W, 2a) and two mixed-ligand tris chelate complex containing N,N-diethyldithiocarbamate, [Et₄N]₂[M^IV(Et₂NS₂)(mnt)₂] (M = Mo, 1b; W, 2b) have been synthesized and characterized structurally. Although these complexes are supposed to be quite similar to the well-known symmetric tris chelate complexes of maleonitriledithiolate (mnt), [Et₄N]₂[M^IV(mnt)₃] (M = Mo, 1c; W, 2c), but display both trigonal prismatic and distorted trigonal prismatic geometry in their crystal structure indicating the possibility of an equilibrium between these two structural possibilities in solution. Unlike extreme stability of 1b, 2b, 1c and 2c, both 1a and 2a are highly unstable in solution. In contrast to one reversible reduction in case of 1b and 2b, 1a and 2a exhibited no possible reduction up to −1.2 V and two sequential oxidation steps which have been further investigated with EPR study. Differences in stability and electrochemical behavior of 1a, 1b, 2a and 2b have been correlated with theoretical calculations at DFT level in comparison with long known 1c and 2c.     

Supramolecular assembly driven by hydrogen-bonding and π-π stacking interactions based on copper(II)-terpyridyl complexes

Six 2D and 3D supramolecular complexes [Cu(L1)(O₂CCH₃)₂] · H₂O (1), [Cu₂(L2)₂(μ₂-O₂CCH₃)₂](BF₄)₂ (2), [Cu₂(L1)₂(BDC)(NO₃)₂] · 0.5H₂O (3) [Cu₂(L2)₂(BDC)(NO₃)₂] (4), [Cu₂(L3)₂(BDC)(NO₃)₂] · 0.5H₂O (5) and [Cu₂(L2)₂(BDC)(H₂O)₂](BDC) · 8H₂O (6) (L1 = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine, L2 = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine, L3 = 4′-phenyl-2,2′:6′,2″-terpyridine, BDC = 1,4-benzenedicarboxylate), have been prepared and structurally characterized by X-ray diffraction crystallography. In complexes 1, 3, and 4, 1D channels are formed through C-H?O and C-H?N hydrogen-bonding interactions, and further linked into 3D structure via C-H?O and O-H?O interactions. Complex 2 is a 2D layer constructed from intermolecular C-H?F and π-π stacking interactions. In the structure of 6, the BDC²⁻ ions and solvent water molecules form a novel 2D layer containing left- and right-handed helical chains via hydrogen-bonds, and an unusual discrete water octamer is formed within the layer. In 2, 4, 6 and [Ag₂(L2)₂](PF₆)₂ (7) the bonding types of pendent pyridines of L2 depending on the twist about central pyridines are involved in intramolecular (2 and 4), intermolecular (6) or coordination bonds (7) in-twist-order of 5.8°, 3.7°, 28.2° and 38.0°, respectively. Differently, the pendent pyridines of L1 in 1 and 3 form intermolecular hydrogen bonds despite of distinct corresponding twist angles of 25.1° (1) and 42.6°(3). Meanwhile, π-π stacking interactions are present in 1-6 and responsible for the stabilization of these complexes.