A preparative study of some coronands and their complexation of silver(I), zinc(II), cadmium(II) and lead(II)

A study of the complexation of heavy metal ions by the coronands 3,12,20,29-tetraoxa-35,36-diazapentacyclo[29.3.1.1.^14,18.0^5,10.0^22,27]-hexatriaconta-1(35),5(10),6,8,14,16,18(36),22(27),23,25,31,33-dodecaene (1); 2,3,11,12-bis (4^′-methylbenzo)-1,4,10,13-tetrathia-7,16-dioxacyclo-octadeca-2,11-diene (2); 7,16-diaza-1,4,10,13-tetraoxa-2,3,11,12-dibenzocyclooctadeca-2,11-diene (3); 2-[19-(2-hydroxy-2-phenylethyl)-7,8,9,10, 18,19,20,21-octahydro-6H,17H-dibenzo[b,k][1,4,10,13,7,16]tetraoxadiazacyclooctadecin-8-yl]-1-phenyl-1-ethanol (4); 1,4,10,13-tetraoxa-7,16-diazacyclo-octadecane (5); and 2-[16-(2-hydroxy-2-phenylethyl)-1,4,10,13-tetraoxa-7,16-diazacyclo-octadecanyl]-1-phenyl-1-ethanol (6) is described. Coronands 1 and 3 were prepared by literature methods, improved methods were used to prepare 2, and 4 and 6 were prepared from 3 and 5 (obtained commercially), respectively. Potentiometric studies in N,N-dimethylformamide yielded (logK/dm³ mol⁻¹)=5.50, 6.49, 9.42 and 7.52 for [Ag · 1]⁺, [Ag · 2]⁺, [Ag · 5]⁺ and [Ag · 6]⁺, respectively; <2, <2, 4.30 and <2 for [Zn · 1]²⁺, [Zn · 2]²⁺, [Zn · 5]²⁺ and [Zn · 6]²⁺, respectively, <2, <2, 5.92 and >7.52 for [Cd · 1]²⁺, [Cd · 2]²⁺, [Cd · 5]²⁺, and [Cd · 6]²⁺, respectively, and 2.62, 2.38, 6.71 and >7.52 for [Pb · 1]²⁺, [Pb · 2]²⁺, [Pb · 5]²⁺, and [Pb · 6]²⁺, respectively. ESI-MS studies of the interactions of 1-6 with Ag⁺, Zn²⁺, Cd²⁺ and Pb²⁺ are also reported.     

Weak interionic interactions in 2-bromoimidazolium derivatives

The 2-bromoimidazolium bromide [ImBr]Br (5, Im=2,3-dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) is prepared from Im (4) and bromine. From 4 and CBr₄, the adduct [ImBr]Br · CBr₄ (6) is obtained. 5 reacts with TeBr₄ to give the salt [ImBr][TeBr₅] (7). The crystal structures of 5-7 reveal the presence of weak interionic Br to Br interactions which are discussed on comparison with the structure of [ImI]I (8) and similar compounds.     

Stereospecific interactions between dinuclear complex cations involving square-planar [Pt(II)(μ-S)2(bpy)] (bpy = 2,2′-bipyridine) frameworks derived from optically active octahedral Co(III) units with d- or l-penicillaminates

The reaction of the octahedral mononuclear complex, trans(N)-[Co(l-pen-N,O,S)₂]⁻ (pen = penicillaminate), with [PtCl₂(bpy)] (bpy = 2,2′-bipyridine) stereoselectively gave an optically active S-bridged dinuclear complex, [Pt(bpy){Co(l-pen)₂}]Cl · 3H₂O (2Cl · 3H₂O), whose structure is enantiomeric to the previously reported [Pt(bpy){Co(d-pen)₂}]Cl · 3H₂O (1Cl · 3H₂O). The mixture of equimolar amounts of 1Cl · 3H₂O and 2Cl · 3H₂O in H₂O crystallizes as [Pt(bpy){Co(d-pen)₂}]_0.5[Pt(bpy){Co(l-pen)₂}]_0.5Cl · 7H₂O (3Cl · 7H₂O), in which the enantiomeric complex cations 1 and 2 are included in the ratio of 1:1. The crystal structures of 2Cl · 3H₂O and 3Cl · 7H₂O were determined by X-ray crystallography, and compared with that of 1Cl · 3H₂O. The structural feature for 2 is essentially consistent with that for 1, except for the absolute configurations around the octahedral Co(III) center. The optically active complex cation 2 exists as a monomer, accompanied by no intermolecular interactions in the π-electronic systems of bpy moieties. In the crystals of 3Cl · 7H₂O, on the other hand, the enantiomeric complex cations, [Pt(bpy){Co(d-pen)₂}]⁺ and [Pt(bpy){Co(l-pen)₂}]⁺, are arranged alternately while overlapping the bpy planes along a axis, and the π electronic system of the bpy framework in [Pt(bpy){Co(d-pen)₂}]⁺ interacts with those in [Pt(bpy){Co(l-pen)₂}]⁺. Differences between the crystal structures of 2Cl · 3H₂O and3Cl · 7H₂O significantly reflect their diffuse reflectance spectra. In aqueous solution, each cation in both 2Cl · 3H₂O and 3Cl · 7H₂O is comparatively put on a free environment without such intermolecular interactions.     

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.     

Extended molecular networks based on Zn and Cd imparting N-substituted imidazole

Synthesis of complexes with the formulations [M(CPI)₂Cl₂] (M = Zn, 1; M = Cd, 4) and [M(CPI)₆](X)₂ (M = Zn, X = NO₃⁻, 2; X = ClO₄⁻, 3; M = Cd, X = NO₃⁻, 5; X = ClO₄⁻, 6) have been achieved from the reactions of MCl₂, M(NO₃)₂·xH₂O and M(ClO₄)₂·xH₂O (M = Zn, Cd) with 1-(4-cyanophenyl)-imidazole (CPI). Complexes 1-6 have been characterized by elemental analyses and spectral studies (IR, ¹H, ¹³C NMR, electronic absorption and emission). Molecular structures of 1, 2, 3 and 6 have been determined crystallographically. Weak interaction studies on the complexes revealed presence of various interesting motifs resulting from C-H···N, C-H···Cl and π-π stacking interactions. The complexes under study exhibit strong luminescence at ∼450 nm in DMSO at room temperature.     

Ruthenium(VI) and osmium(VI) nitrido complexes with halogenated phenoxide and thiophenoxide ligands

Treatment of [Buⁿ₄N][Ru(N)Cl₄] with Na(OR) afforded [Buⁿ₄N][Ru(N)(OR)₄] (R = C₆F₅ (1), C₆F₄H (2), C₆Br₅ (3)), whereas that with [Buⁿ₄N][Os(N)Cl₄] gave [Buⁿ₄N][Os(N)(OR)₃Cl] (R = C₆F₅ (4), C₆F₄H (5), C₆Br₅ (6)). Treatment of [Buⁿ₄N][M(N)Cl₄] with Na(SC₆F₄H) and Na(Sxyl) (xyl = 2,6-dimethylphenyl) afforded [Buⁿ₄N][M(N)(SC₆F₄H)₄] (M = Ru (7), Os (8)) and [Buⁿ₄N][M(N)(Sxyl)₄] (M = Ru (9), Os (10)), respectively. The crystal structures of compounds 1, 6 and 9 have been determined.     

Oxime-functionalized diazamesocyclic derivates and their metal complexes: Effect of the ligand backbones and anions on the generation of novel monomeric and mono-μ-Cl dimeric Cu complexes

Two oxime-functionalized diazamesocyclic derivates, namely, N,N′-bis(acetophenoneoxime)-1,4-diazacycloheptane (H₂L¹) and N,N′-bis(acetophenonoxime)-1,5-diazacyclooctane (H₂L²), have been prepared and characterized. Both ligands (obtained in the hydrochloride form) can form stable metal complexes with Cu^II and Ni^II salts, the crystal structures of which were determined by X-ray diffraction technique. The reactions of H₂L¹ with Cu(ClO₄)₂ and Ni(ClO₄)₂ afford a penta-coordinated mononuclear complex [Cu(H₂L¹)Cl] · ClO₄ (1) and a four-coordinated monomeric [Ni(HL¹)] · ClO₄ (2), in which the ligand is monodeprotonated. The ligand H₂L² also forms a quite similar mononuclear [Ni(HL²)] · ClO₄ complex with Ni(ClO₄)₂, according to our previous work. However, reactions of different Cu^II salts [Cu(ClO₄)₂, CuCl₂ and Cu(NO₃)₂ for 3, and CuSO₄ for 4] with H₂L² in the presence of NaClO₄ yield two unusual mono-μ-Cl dinuclear Cu^II complexes [Cu₂(HL²)₂Cl] · (ClO₄) (3), and [Cu₂(H₂L²)(HL²)Cl] · (ClO₄)₂ · (H₂O)(4). These results indicate that the resultant Cu^II complexes (1, 3 and 4) are sensitive to the backbones of diazamesocycles and even auxiliary anions.     

Silver(I), mercury(II) and palladium(II) complexes of functionalized N-heterocyclic carbenes: Synthesis, structural studies and catalytic activity

A series of NHC silver(I), mercury(II) and palladium(II) complexes, [(1,3-diethylbimy)₆Ag₄I₃]I (2), [(1-benzyl-3-picolylbimy)Ag₂Br₂]_n (3), [(1-benzyl-3-picolylbimy)HgI(CH₂CN)]₂ (4), {[(1-picolyl-3-npropylbimy)₂Hg][Hg₂I₆]}_n (5) and [(1,3-dipicolylbimy)PdCl]Cl (6), as well as one anionic complex [1,3-diethylbimidazolium]₂[HgI₄] (1) (bimy = benzimidazol-2-ylidene), have been prepared and characterized. Interestingly, a wind wheel-like Ag₄I₃ arrangement in 2 is formed, 1D polymeric chain containing 12-membered macrometallocycles and quadrangle Ag₂Br₂ units in 3 is generated, and the α-carbon atom of deprotonated acetonitrile ([CH₂CN]⁻) in 4 participates in coordination with mercury(II) atom. In the crystal packings of complexes 1-6, 2D supramolecular layers or 3D supramolecular architectures are formed via intermolecular weak interactions, including π-π interactions, hydrogen bonds, C-H···π contacts, weak Hg···I bonds and I···I bonds. Additionally, the catalytic activity of the NHC palladium(II) complex 6 in Suzuki-Miyaura cross-coupling reaction was studied.     

Mimicking the reduced, oxidized and azide inhibited form of manganese superoxide dismutase by mononuclear Mn compounds utilizing tridentate ligands

The manganese complexes [Mn^II(Hbmimpm)₂(NO₃)](NO₃) · Et₂O (1), [Mn^III(bmimpm)₂(OAc)] · 2CH₂Cl₂(2), and [Mn^III(bmiapm)₂(OAc)] · MeOH · H₂O · CH₂Cl₂(3) containing the new ligands Bis(1-methylimidazol-2-yl)-(4-methoxyphen-1-yl)methanol (Hbmimpm) and Bis[(1-methylimidazol-2-yl)](2-aminophenyl)methanol (Hbmiapm) were synthesized. They are good structural models for the reduced (1) and oxidized (2, 3) form of manganese superoxide dismutase. All complexes were characterized by spectroscopic methods and X-ray structure analysis. Compounds 1 and 2 crystallize in the monoclinic space group P2₁/c whereas complex 3 crystallizes in the monoclinic space group P2₁/n. The coordination sphere around the manganese cores is distorted octahedral with two corresponding tridentate ligands representing the protein ligands and one nitrate (1) or acetate (2, 3) ion occupying two cis positions. Similar to the enzyme the Mn(III) complex 2 reacts with sodium azide. The obtained microcrystalline azide adduct was characterized by UV-Vis and IR spectroscopy.     

Syntheses and characterization of five d coordination polymers derived from phenanthroline derivative and dicarboxylate mixed ligands

Five structurally diverse complexes, [Cd₂(pyip)₂(suc)₂]_n·1.5nH₂O (1), [Zn(pyip)(glu)]_n (2), [Cd(pyip)(glu)]_n (3), [Zn(pyip)₂(adip)₂]_n·2.5nH₂O (4), [Cd₃(pyip)₂(adip)₃]_n (5) (pyip = 2-(pyridin-3-yl)-1H-imidazo[4,5-f][1,10]phenan-throline, H₂suc = succinic acid, H₂glu = glutaric acid, H₂adip = adipic acid), have been hydrothermally synthesized. Complexes 1 and 4 are ribbon-like chains, in which pyip ligands attach to the both sides of the chain in pairs. Complex 2 is a one dimensional (1D) wave-like chain, while the pyip ligands attach to only one side of the chain. Complexes 3 and 5 are both two dimensional (2D) networks, in which the dicarboxylate ligands connect the dinuclear or trinuclear Cd^II units into layers with (4, 4) topological network. The structural differences among these complexes show that the organic acids have important influences on the final structures.     

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).     

Coordination chemistry of heterocycle-functionalized diazamesocycles: tuning the productive Ni complexes through altering the pendants of ligands

In order to further understand the coordination chemistry of diazamesocyclic systems, a series of mononuclear Ni^II complexes with 1,4-diazacycloheptane (DACH) functionalized by additional imidazole or pyridine donor pendants, including [NiL¹](ClO₄)₂ · H₂O (1), [NiL¹Cl](ClO₄) (2), [NiL²Cl](ClO₄) · CH₃OH (3), [NiL²Cl][NiL²](ClO₄)₃ (4) and [NiL³](ClO₄)₂ (5), where L¹ = 1,4-bis(N-1-methylimidazol-2-yl-methyl)-1,4-diazacycloheptane, L² = 1,4-bis(pyridyl-2-yl-methyl)-1,4-diazacycloheptane, and L³ = 1,4-bis-(imidazol-4-yl-methyl)-1,4-diazacycloheptane, have been prepared and characterized. A detailed study on the solid structures and solution spectra of these complexes indicates that tetradentate ligands L¹, L² and L³ would lead to new Ni^II complexes with different coordination environments in the solid states and solution. The N-methyl substituted imidazole functionalized ligand L¹ forms green compound 2 and yellow product 1; while the pyridine functionalized ligand L² affords red product 4 and green complex 3; the ligand L³ results in only one stable mononuclear Ni^II product 5. The solution behaviors of these interesting compounds were also investigated by UV-Vis technique.     

Porous copper(I) complexes of 2,11-dithia[3.3]paracyclophane: desorption and adsorption of guest molecules

Four copper(I) complexes of 2,11-dithia[3.3]paracyclophane (dtpcp), [CuI(dtpcp)] · MeCN (1), [CuBr(dtpcp)] · MeCN (2), [CuCl(dtpcp)] · MeCN (3) and [Cu₂I₂(dtpcp)₂] · Me-thf (4) (Me-thf=2-methyltetrahydrofuran), have been synthesized and their molecular structures determined by X-ray crystallography. Complexes 1 and 2 are isostructural, and exhibit 3D networks with elliptical channels along a-axis, which are constructed by dtpcp molecules bridging zigzag CuI and CuBr chains, respectively. Complexes 3 and 4 are 2D porous sheet networks constructed by bridging the zigzag copper-dtpcp chains via rhombic ring of Cu₂X₂ (X=Cl or I). All sheets in 3 are packed in an eclipsed manner through π-π stackings to generate channels along the a-axis. However, the 2D porous sheets in 4 are packed in an offset mode such that channels are not formed along c-axis. Complexes 1 and 2 can reversibly incorporate guest acetonitriles without collapse of structures, and the original frameworks of 1 and 2 are completely recovered after incorporation of guests which are confirmed by X-ray powder diffraction (XRPD) pattern and ¹H NMR spectrum. Additionally, complex 1 exhibits selectivity in size and polarity for guest inclusion.     

Transition metal complexes based on pyridine ligand containing both bis(2-pyridyl) and 1,3-dithiole-2-ylidene units: Syntheses, structures, and magnetic studies

Two new mononuclear spin-crossover iron(II) complexes, [FeL₂(NCS)₂] · H₂O (1) and [FeL₂(NCSe)₂] (2), have been synthesized from the reaction of the versatile ligand 4,5-bis(2-cyanoethylthio)-2-bis(2-pyridyl)methylene-1,3-dithiole (L), Fe(ClO₄)₂, and KNCX (X = S/Se). Reactions of L with Cu^II or Co^II salts afford one mononuclear complex [CuL(hfac)₂] · CH₃OH (hfac = hexafluoroacetylacetonate) (3), one dinuclear complex [(CuLCl)₂(μ-Cl)₂] · CH₃OH (4), and two 1D chain species, [CuL₂]_n(BF₄)_2n (5) and [CoL₂]_n(ClO₄)_2n · 2nCH₂Cl₂ (6). The crystal structures of complexes 1 and 3-6 have been determined by X-ray crystallography. Short intermolecular S?S contacts between neighboring 1D arrays are observed in 5 and 6, which lead to the formation of the 2D structure. The magnetic properties are studied, and antiferromagnetic couplings between the Cu^II centers across the chloride bridges have been found in 4 (J = 2.04 cm^-1). Spin-crossover behaviors between high and low spin states are observed at T_1/2 = 80 K for 1 and T_1/2 = 300 K for 2, respectively.     

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.     

[S2], [S3], and [N3] coordination modes of hydrotris(thioxotriazolyl)borato. Zinc, nickel, cobalt, and bismuth complexes

The ligand hydrotris(1,4-dihydro-3-methyl-4-phenyl-5-thioxo-1,2,4-triazolyl)borato (Tr^Ph,Me) was synthetized as natrium salt and the complexes [Zn(Tr^Ph,Me)₂] · 7.5H₂O · 1.5CH₃CN (2a), [Zn(Tr^Ph,Me)₂] · 8DMF (2b), [Co(Tr^Ph,Me)₂] · 8DMF (3a), [Ni(Tr^Ph,Me)₂] · H₂O · 6DMSO (4a), [Bi(Tr^Ph,Me)₂]NO₃ (5), have been isolated and structurally characterized by X-ray diffraction. In the zinc derivatives the ligand adopts different denticity and coordination modes, η² and [S₂] for 2a and η³ and [N₃] for 2b, depending on the crystallization solvent, giving rise to tetrahedral and octahedral geometry, respectively. In the octahedral cobalt and nickel complexes the ligand is η³ and [N₃] coordinated whereas in the bismuth complex the η³ and [S₃] coordination is exhibited.     

Diverse coordination of polynuclear copper(II) complexes constructed from benzene tetracarboxylates

The reaction of aqueous solutions of the preformed 1:1 Cu(ClO₄)₂-polydentate amine with tetrasodium 1,2,4,5-benzene tetracarboxylate (Na₄bta) afforded three different types of polynuclear compounds. These include the tetranuclear complexes: [Cu₄(Medpt)₄(μ₄-bta)(ClO₄)₂(H₂O)₂](ClO₄)₂·2H₂O (1), [Cu₄(pmdien)₄(μ₄-bta)(H₂O)₄](ClO₄)₄ (2), [Cu₄(Mepea)₄(μ₄-bta)(H₂O)₂](ClO₄)₄(3), [Cu₄(TPA)₄(μ₄-bta)](ClO₄)₄·10H₂O (4) and [Cu₄(tepa)₄(μ₄-bta)](ClO₄)₄·2H₂O (5), the di-nuclear: [Cu₂(DPA)₂(μ₂-bta)(H₂O)₂]·4H₂O (6), [Cu₂(dppa)₂(μ₂-bta)(H₂O)₂]·4H₂O (7) and [Cu₂(pmea)₂(μ₂-bta)]·14H₂O (8) and the trinuclear complex [Cu₃(dppa)₃(μ₃-bta)(H₂O)_2.25](ClO₄)₂·6.5H₂O (9) where Medpt = 3,3′-diamino-N-methyldipropylamine, pmedien = N,N,N′,N″,N″-pentamethyldiethylenetriamine, Mepea = [2-(2-pyridyl)ethyl]-(2-pyridylmethyl)methylamine, TPA = tris(2-pyridylmethyl)amine, tepa = tris[2-(2-pyridyl)ethyl)]amine, DPA = di(2-pyridymethyl)amine, dppa = N-propanamide-bis(2-pyridylmethyl)amine and pmea = bis(2-pyridylmethyl)-[2-(2-pyridylethyl)]amine. The complexes were structurally characterized by elemental analyses, spectroscopic techniques, and by X-ray crystallography for complexes 1, 2, 4, 6, 7 and 9. X-ray structure of the complexes reveal that bta⁴⁻ is acting as a bridging ligand via its four deprotonated caboxylate groups in 1, 2 and 4, three carboxylate groups in 9 and via two trans-carboxylates in 6 and 7. The complexes exhibit extended supramolecular networks with different dimensionality: 1-D in 2 and 4 due to hydrogen bonds of the type O-H···O, 2-D in 1 and 7, and 3-D network in 6 as a result of hydrogen bonds of the types N-H···O and O-H···O. Magnetic susceptibility measurements showed very weak antiferromagnetic coupling between the Cu^II ions in 1-5, 7-9 (|J| = 0.02-0.87 cm⁻¹) and weak ferromagnetic coupling for 6 (J = 0.08 cm⁻¹).     

Syntheses, crystal structures and magnetic properties of trinuclear and [3 × 1 + 1 × 2] pentanuclear complexes derived from a compartmental ligand: Role of solvent on nuclearity and number of components

Reaction of [Cu^IIL⊂(H₂O)] (H₂L = N,N′-ethylenebis(3-ethoxysalicylaldimine)) with nickel(II) perchlorate in 1:1 ratio in acetone produces the trinuclear compound [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂ (1). On the other hand, on changing the solvent from acetone to methanol, reaction of the same reactants in same ratio produces the pentametallic compound [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂·2[Cu^IIL⊂(H₂O)]·2MeOH (2A), which loses solvated methanol molecules immediately after its isolation to form [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂·2[Cu^IIL⊂(H₂O)] (2B). Clearly, formation of 1 versus 2A and 2B is solvent dependent. Crystal structures of 1 and 2A have been determined. Interestingly, compound 2A is a [3 × 1 + 1 × 2] cocrystal. The cryomagnetic profiles of 1 and 2B indicate that the two pairs of copper(II)···nickel(II) ions in the trinuclear cores in both the complexes are coupled by almost identical moderate antiferromagnetic interaction (J = −22.8 cm⁻¹ for 1 and −26.0 cm⁻¹ for 2B).     

Synthesis, characterization, and cytotoxicity of trimethylplatinum(IV) complexes with 2-thiocytosine and 1-methyl-2-thiocytosine ligands

The reaction of [PtMe₃(MeOH)(bpy)][BF₄] (1) with the thionucleobases 2-thiocytosine (SCy, 2) and 1-methyl-2-thiocytosine (1-MeSCy, 3) resulted in the formation of the complexes [PtMe₃(bpy)(SCy-κS)][BF₄] (4) and [PtMe₃(bpy)(1-MeSCy-κS)] [BF₄] (5), respectively. The complexes were characterized by ¹H and ¹³C NMR spectroscopy as well as by single-crystal X-ray analyses of 4 · MeOH and 5. In 4 · MeOH two strong hydrogen bonds (N4-H?N3′: N4?N3′ 2.976(7) Å) between the thiocytosine ligands give rise to base pairing thus forming dinuclear cations [{PtMe₃(bpy)(SCy-κS)}₂]²⁺. In both complexes the platinum atom is octahedrally coordinated [PtC₃N₂S] by three methyl ligands, the 2,2′-bipyridine ligand and the κS coordinated nucleobase (configuration index: OC-6-33). The structural investigations gave evidence that the sulfur atoms of the nucleobase ligands in 4 · MeOH and 5 have to be regarded as sp³ and sp² hybridized, respectively. Thus, the ligand in 4 · MeOH has to be considered as the deprotonated thiol-amino form of thiocytosine being reprotonated at N1. In complex 5 the 1-MeSCy is coordinated in its thione-amino form. DFT-calculations of the base-paired dinuclear cation in 4 as well as of 4 itself gave proof of the strength of the hydrogen bond (8.5 kcal/mol) and exhibited that cation-anion interactions influence the conformation of the complex. In vitro cytotoxicity studies of 4 and 5 using nine different human tumor cell lines revealed moderate cytotoxic activity.     

Versatile reaction of the potential host system [(Me3Sn) 4Ru(CN) 6]∞ with 4-thiopyridone/4-mercaptopyridine in water

Single crystals of three derivatives of the structurally still incompletely characterized coordination polymer [(Me₃Sn)₄Ru(CN)₆] 1b have been prepared and subjected to crystallographic studies: [1b · 4H₂O]=2b forms stacks of puckered _∞²[Ru{μ-CNSn(Me₃)NC}₂] sheets interlinked by hydrogen bonds in making use of two additional CNSn(Me₃)OH₂ ligands and quasi-zeolitic water. Mild drying of 2b leads to the “missing link” between 1b and 2b, [1b · 2H₂O], 3b. The structure of [1b · 2tp] (tp=4-thiopyridone) consists of a three-dimensional, negatively charged host framework comprising (via Sn-S bonds) one “aromatic” thione linkage and a [Me₃Sn · tp]⁺guest ion involving a more zwitterionic form of tp. Slow uptake of Me₃SnCl from the gas phase by an aqueous solution of K₄[Ru(CN)₆] and tp afforded the novel assembly [1b · 2H₂O · 0.8pms · 0.2pds] (pms/pds=4,4^′-dipyridylmono-/disulfide), the supramolecular architecture of which resembles that of 2b. Bridging pms or pds molecules occupy equivalent interlayer sites, and the pms/pds ratio is likely to vary. At least three further assemblies containing again 1b and either tp or pds/pms have likewise been isolated, however, not as single crystals.