Macrocyclic dinuclear gold(I) and silver(I) NHCs complexes

The ligands bis-(imidazolium) hexafluorophosphate (Himy = -C₃N₂H₃-, imidazolium; R = 1-naphthylmethylene, 1a; 9-anthracenylmethylene, 1b) with an oxoether chain were easily prepared by the reaction of substituted imidazole with the diglycol diiodide, followed by exchange of anions with . 1a and 1b reacted with Ag₂O in DMSO or CH₃CN to yield [2 + 2] dinuclear Ag(I) NHCs macrocyclic complexes 2a and 2b, which showed much different conformation in solid corresponding to the R- substituent. Carbene transmetalation reactions of 2a-b with Au(SMe₂)Cl give dinuclear Au(I) analogs 3a and 3b. The new NHCs complexes were characterized by elemental analyses, ¹H NMR, ¹³C NMR and the structures of 2a-b and 3a were confirmed by X-ray diffraction determination.     

Impact of counteranion on the self-assembly of Cd(II)-containing MOFs: Syntheses, structures and photoluminescent properties

Three Cd(II)-containing metal-organic frameworks based on 1,1′-(1,5-pentanediyl)bis-1H-benzimidazole (pbbm), namely, , [CdSO₄(pbbm)₂]_n (2) and [CdI₂(pbbm)]₂ (3) are prepared systematically by using hydrothermal technique to examine the effects of counteranion on the topology of the resultant network. In complexes 1 and 2, pbbm acts as a bidentate ligand to link two Cd atoms to result in two different 1D chain structures. Complex 3 has a dimeric structure in which two Cd(II) cations are bridged by two pbbm ligands. The significant differences of these MOFs indicate that the counteranions have great impact on the assembling and structures of the resultant MOFs. The photoluminescent properties of these new materials have been studied in the solid state at room temperature. Further investigation reveals that their photoluminescent characteristics obtained from experiments accord with the computed parameters.     

Synthesis of Fe(II) and Cu(II) building blocks for metal-organic frameworks

In situ reaction of the aminobenzoic acids 2-aminobenzoic acid and 3,5-diaminobenzoic acid with salicylaldehyde provide easy access to the ligands 2-[{(2-hydroxyphenyl)methylene}amino]benzoic acid (L1) and 3,5-bis[{(2-hydroxyphenyl)methylene}amino]benzoic acid (L2). Addition of a Fe(II) or Cu(II) salt to the solution of the ligand yields the corresponding Fe and Cu complexes. The species synthesized have been structurally characterized by single-crystal X-ray diffraction. The Fe(II) complex [Fe(L1)(MeOH)₃] (1) crystallizes in the triclinic space group . The Cu(II) complex [Cu(L1)] (2) is a one-dimensional chain and crystallizes in the monoclinic space group P2₁. The Cu(II) complex [Et₃NH]₂[Cu₂(L2)₂] (3) crystallizes in the monoclinic space group P2₁/n. The magnetic properties of 1, 2 and 3 have been studied, showing that the Cu(II) ions of 2 and 3 are ferromagnetically coupled. Complexes 1 and 3 have strong potential as metal-bearing building blocks for the synthesis of metal-organic frameworks.     

Crystal structure of six and seven coordinate manganese(II) complexes with penta and hexadentate pyridylmethyl ligands

Two six-coordinated manganese(II) complexes [Mn(pydien)Cl](ClO₄) · C₂H₅OH (1), [Mn(pydien)NCS](ClO₄) (2) and two seven-coordinated manganese(II) complexes [Mn(pydado)Cl](ClO₄) (3), [Mn(pydado)NCS](ClO₄) (4) have been obtained using linear penta and hexadentate ligands pydien and pydado (pydien: 1,7-bis(2-pyridylmethyl)-1,4,7-triazaheptane and pydado: 1,10-bis(pyridylmethyl)-1,10-diaza-4,7-dioxadecane). The crystal structures for all compounds have been determined. 1 and 3 crystallize in the triclinic space group , 2 crystallizes in the orthorhombic space group Pbca, whereas 4 crystallizes in the monoclinic space group P2₁/c. The bound anion (chloro or isothiocyanato) in complexes 1 and 2 has no influence on the geometry of six-coordinate manganese(II) complexes, whereas the geometry and the wrapping of the hexadentate ligand (pydado) around Mn²⁺ cation depend on the nature of the bound anion. The complex 3 has a capped octahedron geometry with the two pyridyl groups in trans position, while the geometry of complex 4 can be described as pentagonal bipyramid with one pyridyl group and a thiocyanate anion in the axial positions.     

Synthesis and structures of pyridinecarboxylate-containing zinc(II) complexes in dien and tren system

Four new zinc(II) complexes [Zn(dien)(μ-nic)]₂(BPh₄)₂·2CH₃OH (1), {[Zn(dien)(isonic)]BPh₄}_n (2), [Zn(tren)(nic)]BPh₄ (3) and [Zn(tren)(isonic)]BPh₄ (4) (dien/tren = diethylenetriamine/triethylenetriamine, nic/isonic = nicotinate/isonicotinate anion) were synthesized and structurally characterized by IR, ¹H NMR and single crystal X-ray diffraction. In the zinc(II) complexes of dien, both nicotinate and isonicotinate connect the zinc(II) ions via N,O-bis-monodentate mode. Complex 1 contains a centrosymmetric dinuclear unit bridged by two nicotinate anions in anti-parallel way. Complex 2 is characterized by an infinite one-dimensional zigzag chain bridged by isonicotinate anion in an end-to-end mode. The Zn···Zn distance is 6.782 for 1 and 8.805 Å for 2. While in the complexes of tren, both 3 and 4 are mononuclear complexes with nicotinate and isonicotinate coordinated to zinc(II) ion through only one oxygen atom of their carboxylate groups. The zinc(II) ions in all of the four complexes are in a distorted trigonal bipyramidal geometry. Complex 3 forms a dinuclear unit and complex 4 forms an infinite 2D sheet structure through intermolecular H-bonds. In all of the crystal lattices, the counterions act to balance the electronic charge at the same time to construct different 3D structures through noncovalent interactions such as C-H···π, N-H···π and van der Waals interactions.     

Target syntheses of saturated Keggin polyoxometalate-based extended solids

By the approach of target synthesis, three infinitely extended hybrid compounds based on the saturated Keggin polyoxoanions have been synthesized under hydrothermal conditions: , and (phen = 1,10-phenanthroline, trea = triethylamine). The isostructural compounds 1 and 2 belong to the monoclinic space group P2₁/c and both contain neutral 2D layers and discrete polyoxometalate clusters decorated by transitional metal complexes. They represent an important example of the family of intercalated solids, in which both the 2D layers and the intercalated molecules are polyoxometalates with covalently linked transitional metal complex fragments. Compound 3, crystallizing in the monoclinic space group C2/c, consists of 1D zigzag chains constructed from alternating polyoxoanions and [Ni(phen)₂]²⁺ fragments. More interestingly, these three compounds are constructed directly from saturated polyoxometalates, in which the intact skeletons of Keggin clusters are maintained under hydrothermal conditions. Variable-temperature magnetic susceptibility measurements of compounds 1 and 2 reveal the feature of antiferromagnetic exchange interaction in these compounds.     

[Ir(acac)(η-C8H14)2]: A precursor in the synthesis of cyclometalated iridium(III) complexes

A new convenient synthesis and the crystallographic characterization of [Ir(acac)(coe)₂] (2, acac = acetylacetonato; coe = cis-cyclooctene) are described. The title compound crystallized from THF/ethanol in two modifications (monoclinic P2₁/c, 2a, and triclinic , 2b). Complex 2 represents an efficient starting material in the synthesis of mononuclear iridium(III) complexes containing cyclometalated 2-phenylpyridinato ligands using oxidative addition reactions of the corresponding ligands towards 2. Thus [Ir(acac)(ppy)₂] (3, ppy = 2-phenylpyridinato) and [Ir(ppy)₃] (4) (mer, 4a; fac, 4b) were prepared in excellent yields and short reaction times in a kind of one-pot procedure starting from [{Ir(μ-Cl)(coe)₂}₂] (1). Furthermore a convenient synthesis of [{Ir(μ-Cl)(ppy)₂}₂] (5) from 1 and Hppy is described.     

Molecular structures of nickel(II) monochelates of a racemic tridentate ligand and co-ligand induced structural variations

Using a racemic mixture of the tridentate ligand, (((2-pyridyl)ethylamine)methyl)phenolate ion (L⁻) and , NCS⁻, (NC)₂N⁻, OAc⁻ as coligands, complexes having the formula [Ni(L)(N₃)] (1), [Ni(L)(NCS)]₂ (2), [Ni₂(L)₂(OAc)(N(CN)₂)]_n (3) were prepared and structurally characterized. In 1, Ni(II) has a square planar geometry and phenolate oxygen is involved in dipolar ?N^δ+ interaction with electrophilic central nitrogen atom of coordinated azide ion. Complex 2 is dimeric in nature and nickel(II) is penta-coordinated. Compounds 1 and 2 exist as centrosymmetric dimers made up of a pair of R and S enantiomers of L. In 3, an acetate and phenoxo bridged dinickel complex is present which is further linked to a zig-zag coordination polymer by the dicyanamide ion. In a given chain of 3, both L have same enantiomeric form and either RR or SS dimers are repeated along the chain. The magnetic properties are described.     

Syntheses and molecular structures of 6-halogeno-pyridin-2-olate complexes with the diruthenium(2+) core

The complexes [Ru₂(CO)₅(μ-FpyO)₂]₂ (1), [Ru₂(CO)₄(μ-ClpyO)₂]₂ (2), and [Ru₂(CO)₄(μ-BrpyO)₂]₂ (3) were prepared from Ru₃(CO)₁₂ and 6-fluoro-2-hydroxypyridine (FpyOH), 6-chloro-2-hydroxypyridine (ClpyOH) and 6-bromo-2-hydroxypyridine (BrpyOH), respectively, in hot toluene. Compounds 1-3 are coordination dimers with a cyclo-RuORuO motif. By carrying out the reaction in hot methanol, the dinuclear complexes [Ru₂(CO)₄(μ-ClpyO)₂(CH₃OH)] (4) and [Ru₂(CO)₄(μ-BrpyO)₂(CH₃OH)] (5), respectively, were obtained. Treatment of 2 and 3 with triphenylphosphane provided the complexes [Ru₂(CO)₄(μ-ClpyO)₂(PPh₃)] (6) and [Ru₂(CO)₄(μ-BrpyO)₂(PPh₃)] (7), respectively. The solid-state structures of complexes 1, 2, 4, 6, and 7 were determined by single crystal X-ray diffraction. In all cases, a head-head coordination of the two 6-halopyridinolate ligands at the core was found. In all chlorine- or bromine-containing complexes, the axial coordination site at the ruthenium atom neighbored by two Cl or Br atoms remains unoccupied due to steric shielding by the halogen atom. In the fluoropyridinolate complex 1, the same coordination site is occupied by a carbonyl ligand.     

Coordination and derivatization of 3, 4, and 6-membered nitrogen heterocycles at a chiral tungsten(II) center

Reaction of [Tp′W(CO)₂(PhCCPh)][OTf] (1b) (Tp′ = hydridotris(3,5-dimethylpyrazolyl)borate) with excess aziridine or 2-methylaziridine followed by protonation with produces chiral tungsten(II) amine complexes (3, 4; R = Me, Ph). An azetidine amido complex, Tp′W(CO)(PhCCMe)(H₂) (5) is synthesized by reaction of [Tp′W(CO)₂(PhCCMe)][OTf] (1a) with excess azetidine. Oxidation of amido complex 5 with I₂ in the presence of a weak base provides the corresponding 1-azetine complex, (6). Addition of methylmagnesium bromide to complex 6 results in formation of predominantly one diastereomer (S_WR_C/R_WS_C) (96:4 dr) of the 2-methylazetidine complex, Tp′W(CO)(PhCCMe)(H₂) (7). Reaction of complex 5 with results in formation of a cationic azetidine complex, (8). Reaction of 1b with excess piperidine followed by oxidation affords 2,3,4,5-tetrahydropyridine complex 9b, . Formation of an enamido complex, Tp′W(CO)(PhCCPh)(H₂) (10), is observed upon addition of base to 9b. Subsequent addition of [D⁺] to the enamido β-carbon results in the formation of the deuterated product, 9b-d₁, as determined by ²H NMR. Seven X-ray crystal structures have been determined, and these encompass complexes with 3, 4, and 6-membered heterocyclic ligands. Crystal structures are reported for two aziridine adducts (2, 4) two neutral amido complexes (5, 7), one cationic imine complex (6), and one cationic amine (8) complex derived from azetidine, and the imine complex formed from piperidine (9).     

Synthesis and characterization of new AMTTO-imine-ligands and their silver(I) complexes: crystal structures of TAMTTO, [Ag2(TAMMTO)4](NO3)2 · 4MeOH, [Ag(TAMTTO)(PPh3)2]NO3 · 1.5THF, [Ag(FAMTTO)(PPh3)2]NO3

Reaction of 4-amino-6-methyl-1,2,4-triazin-thione-5-one (AMTTO, 1) with 2-thiophenecarboxaldehyde and 2-furaldehyde led to the corresponding iminic compounds 6-methyl-4-[thiophene-2-yl-methylene-amino]-3-thioxo-[1,2,4]-triazin-3,4-dihydro(2H)-5-one (TAMTTO, 2) and 4-[furan-2-yl-methylene-amino]-6-methyl-3-thioxo-[1,2,4]-triazin-3,4-dihydro(2H)-5-one (FAMTTO, 3). Treatment of 2 with AgNO₃ gave the complex [Ag₂(TAMMTO)₄](NO₃)₂ · 4MeOH (4) and of 2 and 3 with [Ag(PPh₃)₂]NO₃ gave the complexes [Ag(TAMTTO)(PPh₃)₂]NO₃ · 1.5THF (5) and [Ag(FAMTTO)(PPh₃)₂]NO₃ (6), respectively. All the compounds have been characterized by elemental analyses, IR spectroscopy and mass spectrometry. Compound 2 and all the complexes have been characterized by X-ray diffraction studies, respectively. In addition, 5 and 6 have been characterized by ³¹P NMR spectroscopy. Crystal data for 2 at −80 °C: monoclinic, space group C2/c, a=2319.6(2), b=609.8(1), c=1673.6(2) pm, β=106.14(1)°, Z=8, R₁=0.0523; for 4 at −80 °C: triclinic, space group , a=877.6(1), b=1085.2(1), c=1557.7(2) pm, α=77.14(1)°, β=80.87(1)°, γ=78.18(1)°, Z=1, R₁=0.0407; for 5 at 20 °C: triclinic, space group , a=1151.1(2), b=1225.1(2), c=1887.4(3) pm, α=78.04(1)°, β=86.20(1)°, γ=76.03(1)°, Z=2, R₁=0.0662; for 6 at −80 °C: triclinic, space group , a=1189.7(2), b=1387.8(2), c=1410.9(2) pm, α=94.74(2)°, β=95.12(2)°, γ=112.41(2)°, Z=2, R₁=0.0511.     

Ligand substitution in hexahalorhenate(IV) complexes: Synthesis, crystal structures and magnetic properties of NBu4[ReX5(DMF)] (X = Cl and Br)

The preparation, crystal structures, and magnetic properties of two rhenium(IV) mononuclear compounds of formula NBu₄[ReX₅(DMF)] with X = Cl (1) and Br (2) are reported. 1 and 2 are isostructural complexes which crystallize in the monoclinic system with the space group P2₁/n. The rhenium atom is six-coordinated with five X atoms and a DMF molecule forming a somewhat distorted octahedral surrounding [values of Re-X varying in the ranges 2.317(1)-2.358(1) (1) and 2.495(1)-2.518(1) Å (2)]. Magnetic susceptibility measurements on samples of 1 and 2 in the temperature range 1.9-300 K are interpreted in terms of magnetically isolated spin quartets with large values of the zero-field-splitting (|2D| is ca. 20.2 and 39.2 cm⁻¹ for 1 and 2, respectively).     

Self-assembly of three hetero- and homopolynuclear cyanide bridged complexes of Fe-Cu and Cu: hydrothermal syntheses, structural characterization and properties

Reaction of Cu^II, K₃ [Fe(CN)₆] and bidentate diimine ligands by hydrothermal synthesis under different conditions affords one novel heteronuclear Fe^II-Cu^I complex, (bipy = 2,2′-bipyridine), and two homonuclear Cu^I complexes, [Cu^I(μ-CN)(bipy)]_n (2) and (3) (phen = 1,10-phenanthroline). Although all the three complexes are 1D cyanide bridged helical chains, they have different helicoids of pseudo-square, pseudo-trigonal and head-to-head bistrigonal for 1, 2 and 3, respectively. The structure of 1 is extended to 2D hexagonal meshed layers by the hydrogen bonding between terminal cyanides and lattice water molecules, which also contain π-π interactions between adjacent sheets. Cu^I ions in 1 are distorted trigonal planar coordinated by two bridging cyanides and one terminal cyanide, whereas that in 2 and 3 are pseudo-tetrahedral coordinated by two bridging cyanides and two N atoms of a diimine. Both the latter homometallic polymers exhibit similar chain structure, and these chains are close packed with their six adjacent chains in a parallel fashion along the c-axis to form a honeycomb network. It should be noted that complex 1 is the first cyanide bridged Fe^II-Cu^I complex of helical chain structure. The spectroscopic properties of complexes 1-3 have also been investigated.     

Structural and thermal properties of three novel alkaline earth metal coordination polymers based on 5-hydroxyisophthalate ligand

Three novel coordination polymers [Ca(5-OH-BDC)(H₂O)₃] · H₂O (1), [Sr(5-OH-BDC)(H₂O)₄] · H₂O (2) and [Ba(5-OH-BDC)(H₂O)₃] (3) were obtained by self-assembly of the corresponding alkaline earth metal chlorate with a ligand, 5-hydroxyisophthalic acid (5-OH-H₂BDC), and their structures were determined by X-ray crystallography. The results revealed that complexes 1, 2 and 3 have two-dimensional network with (6, 3) topology observed in the bc plane. Moreover, the two-dimensional layers can be assembled into three-dimensional supramolecular architectures via intermolecular hydrogen bonds. The two carboxylate groups of 5-OH-BDC²⁻ ligand adopt the same coordination mode in complex 1 as that in 2: a μ3-η2:η1 mode and a chelated mode while in complex 3 they coordinate to Ba(II) ions in a μ3-η2:η1 mode and a monodentate mode, which is not observed in previous reports. The constant-volume combustion energies, Δ_cU, of these complexes were determined by a precise rotating-bomb calorimeter at 298.15 K, then their standard enthalpies of combustion, , and the standard enthalpies of formation, , have been calculated.     

Conformational isomerism and hydrogen-bonded motifs of anion assisted supramolecular self-assemblies using Cu/Co salts and pyridine-4-acetamide

Six novel metal-organic complex assemblies constructed from a conformation-flexible ligand - pyridine-4-acetamide (PAT) and inorganic Cu^II and Co^II salts have been synthesized and structurally characterized by single crystal X-ray diffraction analysis. Crystal structure analysis reveals five types of architectures by variation of metal salts. In {[Cu(PAT)₂Cl₂]}_n (1) and {[Co(PAT)₂Cl₂]}_n (3), PAT ligands bridge metal centers to form one-dimensional chains. The chains are extended to three dimensions with the aid of two types of hydrogen bonded motifs () and (12)). {[Cu(PAT)₂(NO₃)](NO₃)(THF)}_n (5) which exhibits two-dimensional coordinating layers forms open channels filled with solvent molecules. In [Cu(PAT)₂Cl₂] (2), [Co(PAT)₂Cl₂] (4) and [Co(PAT)₄(H₂O)₂](NO₃)₂(THF)₂ (6), PAT is observed as a monofunctional ligand. Complex 2 forms one-dimensional hydrogen bonded chains. Crystal structure of complex 4 has a two-dimensional infinite hydrogen-bonded network with and motifs formed by complementary amide-amide hydrogen bonds. [Co(PAT)₄(H₂O)₂](NO₃)₂(THF)₂ (6) crystallizes in centrosymmetric I4₁/a space group. Complex 6 forms chiral channels which are filled with twisted solvent helices and anion helices. Within each channel the solvent helix and the anion helix have the same handedness; and adjacent channels have opposite handedness. Complexes 1, 2 and complexes 3, 4 illustrate examples of conformational supramolecular isomerism in {[Cu(PAT)₂Cl₂]}_∞ and {[Co(PAT)₂Cl₂]}_∞, respectively. In these complexes, changes of PAT conformations and coordination geometry of metal center induced the structural versatility.     

Syntheses, crystal structures, spectroscopic, fluorescence and thermal properties of silver(I) 5,5-diethylbarbiturato complexes with some aminopyridines

Three new silver(I) complexes of 5,5-diethlybarbiturate (barb), [Ag(barb)(apy)]·H₂O (1), {[Ag(μ-ampy)][Ag(μ-barb)₂]}_n (2) and [Ag(barb)(dmamhpy)] (3) [apy = 2-aminopyridine, ampy = 2-aminomethylpyridine and dmamhpy = 2-(dimethylaminomethyl)-3-hydroxypyridine] have been synthesized and characterized by elemental analysis and FT-IR. Single crystal X-ray diffraction analyses showed that complexes 1 and 3 are mononuclear. In 1, the silver(I) ion is linearly coordinated by a barb anion and a ampy ligand, while a bidentate dmamhpy ligand together with an N-coordinated barb anion forms a trigonal coordination geometry around silver(I) in 3. Complex 2 is a one-dimensional coordination polymer in which silver(I) ions are bridged by ampy ligands, leading to a cationic chain . The [Ag(barb)₂]⁻ units contains two N-bonded barb ligands, bridging the silver centers in the cationic and anionic units via the carbonyl O atoms. Thus, complex 2 contains two-coordinated and four-coordinated silver ions. All complexes display hydrogen-bonded network structures and exhibit appreciable fluorescence at room temperature. Thermal analysis (TG-DTA) data are in agreement with the structures of the complexes.     

Synthesis, characterization, and anion selectivity of copper(II) complexes with a tetradentate Schiff base ligand

A new mononuclear Cu(II) complex, [CuL(ClO₄)₂] (1) has been derived from symmetrical tetradentate di-Schiff base, N,N′-bis-(1-pyridin-2-yl-ethylidene)-propane-1,3-diamine (L) and characterized by X-ray crystallography.The copper atom assumes a tetragonally distorted octahedral geometry with two perchlorate oxygens coordinated very weakly in the axial positions.Reactions of 1 with sodium azide, ammonium thiocyanate or sodium nitrite solution yielded compounds [CuL(N₃)]ClO₄ (2), [CuL(SCN)]ClO₄ (3) or [CuL(NO₂)]ClO₄ (4), respectively, all of which have been characterized by X-ray analysis.The geometries of the penta-coordinated copper(II) in complexes 2-4 are intermediate between square pyramid and trigonal bipyramid (tbp) having the Addition parameters (τ) 0.47, 0.45 and 0.58, respectively.In complex 4, the nitrite ion is coordinated as a chelating ligand and essentially both the O atoms of the nitrite occupy one axial site.Complex 1 shows distinct preference for the anion in the order in forming the complexes 2-4 when treated with a mixture. Electrochemical electron transfer study reveals Cu^IICu^I reduction in acetonitrile solution.     

Structural and magnetic characterization of one-dimensional oxalato-bridged metal(II) complexes with 4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole ligand: A supramolecular open-framework

A new family of one-dimensional oxalato-bridged metal(II) complexes with formula {[M(ox)(abpt)]·4H₂O}_n [M^II = Mn (1), Fe (2), Co (3), Zn (4); ox = oxalate dianion; abpt = 4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole] has been synthesized and chemically, structurally and magnetically characterized. The crystal structures of compounds 2-4 have been solved by single crystal X-ray diffraction, whereas complex 1 has been studied by means of X-ray powder diffraction methods. All of them are isomorphous and crystallize in the triclinic space group P. The metal atoms are bridged by bis-bidentate oxalate anions forming zig-zag chains in which bidentate chelating abpt ligands complete the octahedral O₄N₂ donor set. The crystal structures show an open-framework that contains rectangular channels in which easily removable hydrogen bonded ribbons of water molecules are located. The occurrence of antiferromagnetic intrachain interactions for compounds 1-3 was determined by cryomagnetic susceptibility measurements.     

Extended structures of three new coordination polymers based on 1,10-phenanthroline derivatives and 1,4-benzenedicarboxylate mixed ligands: Preparation, structural characterization and properties

Three coordination polymers, namely, [Cd(HOIP)₂(1,4-bdc)] (1), [Cu(HOIP)(1,4-bdc)] (2) and [Cu(PDIP)(1,4-bdc)] (3) (HOIP = 2-(4-hydroxylbenzene) imidazo[4,5-f]1,10-phenanthroline, PDIP = 2-(3-pyridine) imidazo[4,5-f]1,10-phenanthroline, and 1,4-bdc = 1,4-benzenedicarboxylate), have been synthesized under the hydrothermal conditions. All complexes have been characterized by elemental analyses, IR and single-crystal X-ray diffraction. Structural analyses reveal that complex 1 possesses infinite one-dimensional (1D) chain bridged by 1,4-bdc ligands, complexes 2 and 3 both exhibit two-dimensional (2D) (4,4) network structures based on dinuclear [Cu₂O₂] units. However, the weak interactions are different in complexes 1-3. Moreover, the thermal properties of all complexes, fluorescence property of 1, and the electrochemical behavior of 3 are also reported in this paper.     

Unexpected structural and electronic effects of internal rotation in diruthenium paddlewheel complexes containing bulky carboxylate ligands

A series of complexes containing the bulky carboxylate ligand 2,4,6-triisopropylbenzoate (TiPB) of type trans-[Ru₂(TiPB)₂(O₂CCH₃)₂X] [X = Cl (1), PF₆ (2)] and [Ru₂(TiPB)₄X] [X = Cl (3), PF₆ (4)] have been synthesised. The corresponding complexes trans-[Ru₂(TiPB)₂(O₂CCH₃)₂] (5) and [Ru₂(TiPB)₄] (6) were also isolated. Magnetic susceptibility measurements indicate that the diruthenium cores have the expected three (1-4) or two (5 and 6) unpaired electrons consistent with σ²π⁴δ²(δ^∗π^∗)³ and σ²π⁴δ²δ^∗2π^∗2 electronic configurations. Compounds 1-4 and 6 were structurally characterised by X-ray crystallography, and show the expected paddlewheel arrangement of carboxylate ligands around the diruthenium core. The diruthenium cores of complexes 3, 4 and 6 are all distorted to minimise steric interactions between the bulky carboxylate ligands. The Ru-Ru bond length in the complex 6 [2.2425(6) Å] is the shortest observed for a diruthenium tetracarboxylate and, surprisingly, is 0.014 Å shorter than in the analogous complex 4, despite an increase in the formal Ru-Ru bond order from 2.0 (6) to 2.5 (4). This is rationalised in terms of the extent of internal rotation, or distortion, about the diruthenium core. This was supported by density functional theory calculations on the model complexes [Ru₂(O₂CH)₄] and [Ru₂(O₂CH)₄]⁺, that demonstrate the relationship between Ru-Ru bond length and internal rotation. Electrochemical and electronic absorption data were recorded for all complexes in solution. Comparison of the data for the ‘bis-bis’ (1, 2 and 5) and tetra-substituted (3, 4 and 6) complexes indicates that the shortening of the Ru-Ru bond length results in a small increase in energy of the near-degenerate δ^∗ and π^∗ orbitals.