Syntheses, structures and magnetic properties of three 1-D chain metal-nitroxide coordination polymers bridged by e,e-trans-1,4-cyclohexanedicarboxylate

Three new one-dimensional (1-D) chain metal-nitroxide complexes of the formula [M(NIT4Py)₂(e,e-trans-1,4-chdc)(H₂O)₂]_n (M = Co(II) 1, Ni(II) 2 and Zn(II) 3; NIT4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and 1,4-chdc = 1,4-cyclohexanedicarboxylate dianion) have been synthesized and characterized structurally as well as magnetically. The X-ray crystal structure analyses of complexes 1, 2 and 3 reveal that they are isostructural. Three complexes all crystallize in neutral 1-D chains where metal-nitroxide units [M(NIT4Py)₂(H₂O)₂] are linked by the linear 1,4-cyclohexanedicarboxylate dianion. The 1,4-chdc completes the segregation and only possesses the e,e-trans-conformation, although there are both cis- and trans-isomers in the raw material. The magnetic measurements show that complexes 1 and 2 both exhibit weak antiferromagnetic interactions between the metal ions and the nitroxides.     

Two-dimensional Cu and first Pb coordination polymers based on a flexible 1,4-cyclohexanedicarboxylate ligand displaying different conformations and coordination modes

Two novel metal-organic hybrid coordination polymers {[Cu(bpo)(chdc)(H₂O)](H₂O)_0.5}_n (1) and [Pb(chdc)(H₂O)]_n (2) have been synthesized under different conditions and structurally characterized by single-crystal X-ray diffraction technique, where H₂chdc refers to a flexible 1,4-cyclohexanedicarboxylic acid ligand and bpo is 2,5-bis(4-pyridyl)-1,3,4-oxadiazole. Complex 1 has a two-dimensional (2-D) grid-like [11.28 × 13.63 Å²] framework in which the Cu^II centers are extended via bidentate bridging ligands bpo and e,e-trans-chdc along two directions, exhibiting large porous cavities. Coordination polymer 2 represents the first Pb^II complex of H₂chdc in which the larger Pb^II centers are connected by e,a-cis-chdc anions to afford a 2-D close-knit structure.     

Rh and Ir dibenzo[a,e]cyclooctatetraene complexes: Chloro, hydroxo, and mixed Au oxo complexes

New and improved procedures are reported for the synthesis of [M(DBCOT)(μ-Cl)]₂ (M = Rh, Ir; DBCOT = dibenzo[a,e]cyclooctatetraene) from MCl₃(H₂O)_x or [M(COD)(μ-Cl)]₂ and DBCOT. Treatment of [M(DBCOT)(μ-Cl)]₂ with [(LAu)₃(μ-O)]BF₄(L = PPh₃, P^tBu₃) yields the mixed-metal oxo complexes [M(DBCOT)(μ⁴-O)(AuL)₂]₂(BF₄)₂. Dimeric [Rh(DBCOT)(μ-OH)]₂ is obtained from the reaction of [M(DBCOT)(μ-Cl)]₂ with KOH in EtOH/H₂O. All complexes except [Rh(DBCOT)(μ-Cl)]₂ have been structurally characterized by single crystal X-ray diffraction.     

Two new 3D (3,8)-connected metal-organic frameworks based on zinc-triazole secondary building units and benzenetricarboxylate linkers

Two new zinc-triazole-carboxylate frameworks constructed from secondary building units (SBUs), [Zn₅(trz)₄(btc)₂(DMF)₂(H₂O)₂]·2H₂O·DMF (1) and [Zn₄(trz)₃(btc)₂(CH₃CN)(H₂O)]·5H₂O·(Bu₄N) (2), [Htrz = 1,2,4-triazole, H₃btc = 1,2,4-benzenetricarboxylate, Bu₄N = tetrabutylammonium], have been synthesized by solvothermal reactions and characterized by single-crystal X-ray diffraction analyses, X-ray power diffraction, elemental analyses, infrared spectra and thermogravimetric analyses. Both compounds 1 and 2 exhibit 3D (3,8)-connected tfz-d nets with {4³}₂{4⁶.6¹⁸.8⁴} topology symbol built from rod-shaped {[Zn₅(trz)₄]⁶⁺}_n SBUs (1) and {[Zn₄(trz)₃]⁵⁺}_n SBUs (2). In two compounds, rodlike units are connected by btc ligands via different modes. Additionally, solid state fluorescent emission spectra of two compounds show fluorescent properties at room temperature.     

Effect of copper-substitution on the structure and nuclearity of Cu(II)-pyrazolates: from trinuclear to tetra-, hexa- and polynuclear complexes

The influence of terminal ligands on the structure and nuclearity of copper(II)-pyrazolates has been investigated. Exchange of the chloride ligands of [Cu₃(μ₃-X)(μ-pz)₃Cl₃]ⁿ⁻ (X=O, OH; n=2, 1) or [Cu₃(μ₃-Cl)₂(μ-pz)₃Cl₃]²⁻ complexes for cyanate, acetate or bromide ligands maintains the integrity of the triangular species: PPN[Cu₃(μ₃-OH)(μ-pz)₃(NCO)₃], PPN[Cu₃(μ₃-OH)(μ-pz)₃(O₂CCH₃)₃(H₂O)] · H₂O, Bu₄N[Cu₃(μ₃-OH)(μ-pz)₃(O₂CCH₃)₃] · 3H₂O and (Bu₄N)₂[Cu₃(μ₃-Br)₂(μ-pz)₃Br₃] have been prepared and characterized by spectroscopic and X-ray diffraction techniques, respectively. In contrast, tetranuclear complexes (Bu₄N)₂[Cu₄(μ₃-OH)₂(μ-4-X-pz)₂(μ-O₂CPh)₂(O₂CPh)₄] (X=H, Cl, Br, NO₂) and the hexanuclear complex (Bu₄N)₂[Cu₆(μ₃-O)(μ₃-OH)(μ-4-NO₂-pz)₆(μ-O₂CPh)₃(O₂CPh)₂(H₂O)] · (CH₂Cl₂)_0.5 have been obtained on substitution for benzoate ligands. An attempt to partially substitute the chlorides for tert-butoxide ligands, also provided a tetranuclear complex, (Bu₄N)₂[Cu₄(μ-OH)₂(μ-pz)₄Cl₄], without incorporation of the incoming ligand. Similarly, removal of all chloride ions in the absence of an appropriate substituting ligand leads to higher nuclearity metallacycles [Cu(μ-OH)(μ-pz)]_n (n=6, 8, 9, 12, 14).     

Hydrothermal synthesis of two novel three-dimensional cobalt(II) metal-organic frameworks based on polycarboxylate and benzotriazole

The hydrothermal reactions of 1,4-H₂BDC or 1,4-H₂CDC, HBTA, with Co(NO₃)₂ · 6H₂O in basified solvent gave rise to two coordination polymers, Co₅(μ₃-OH)₂(1,4-BDC)₃(BTA)₂ (1), [Co(1,4-CDC)_0.5(BTA)] (2) (1,4-H₂BDC = 1,4-benzenedicarboxylic acid, 1,4-H₂CDC = 1,4-cyclohexanedicarboxylic acid, HBTA = benzotriazole) and characterized by elemental analysis, IR, single-crystal X-ray diffraction and variable-temperature magnetic measurements. Complex 1 crystallizes in the triclinic system, P space group; the structure determination reveals that 1 has a scarcely reported 8-connected 3D self-penetrating structure based on pentanuclear cobalt clusters. Complex 2 is monoclinic system, P2₁/c space group, and the X-ray structural analysis shows that 2 has a 3D infinite network with (4.6⁴.8)(4².6².8²) topology. Complex 1 exhibits moderately antiferromagnetic coupling, while complex 2 indicating strong spin-orbit coupling.     

Two novel three-dimensional coordination polymers based on metal clusters: Hydrothermal syntheses, crystal structures and luminescence

Two novel coordination polymers with interesting supramolecular architecture, [Zn₂(OH)(BTC)(bix)] (1) and [Cd₂(CDC)₂(bix)₂] (2) (H₃BTC = 1,3,5-benzenetricarboxylic acid, H₂CDC = trans-1,4-cyclohexanedicarboxylic acid and bix = 1,2-bis(imidazol-1-ylmethyl)benzene) have been obtained via hydrothermal reaction and characterized by elemental analysis, IR and single-crystal X-ray diffraction. Complex 1 features a 3D network with one of the scarce (3,8)-connected (4³)₂(4⁶.6¹⁸.8⁴) topology based on the rare CdI₂-type layer constructed from secondary building units (SBUs) of zinc clusters. While 2 exhibits a scarcely reported eight-connected 3⁶.4¹⁶.5⁶ net with dinuclear cadmium clusters as secondary building units. The luminescent properties of 1 and 2 along with the bix ligand in the solid state were investigated.     

Synthesis and crystal structure of one-dimensional zinc(II) polymer constructed by salicylate and trans-1,2-bis(4-pyridyl)ethylene

A new zinc(II) compound, [Zn₂(Hsal)₄(4,4′-bpe)₂] · [Zn(Hsal)₂(4,4′-bpe)(DMF)(H₂O)] · CH₃OH (1) (Hsal = salicylate and 4,4′-bpe = trans-1,2-bis(4-pyridyl)ethylene) has been synthesized and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single crystal X-ray diffraction. The crystal structure consists of three independent moieties: [Zn₂(Hsal)₄(4,4′-bpe)₂], [Zn(Hsal)₂(4,4′-bpe)(DMF)(H₂O)], and non-coordinated CH₃OH molecule. In the compound two independent moieties which are connected by 4,4′-bpe to form 1-D chains, respectively, are further expended to accomplish 2-D network through hydrogen-bonding interactions between non-coordinated methanol and coordinated water molecule or carboxylate oxygen atoms of Hsal ligands.     

Mercury(II) acetate/thiocyanate coordination polymers with n-donor ligands, spectroscopic, thermal and structural studies

Three new mercury(II) coordination polymers, [Hg₂(μ-bpa)(μ-SCN)₂(μ-CH₃COO)₂]_n (1), [Hg₂(μ-4-bpdb)_1.5(μ-CH₃COO)(μ_1,1- SCN)(μ_1,3-SCN)(SCN)]_n · CH₃CN (2) and [Hg(μ-3-bpdb)(CH₃COO)₂]_n (3) {(bpa = 1,2-bis(4-pyridyl)ethane, 4-bpdb) = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene and 3-bpdb = 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene, have been synthesized and characterized by CHN elemental analysis and IR spectroscopy. The single crystal X-ray data show the compound 1 is two-dimensional coordination polymer as a result of simultaneously bridging 1,2-bis(4-pyridyl)ethane, acetate and thiocyanate ligands. The single-crystal X-ray data of the compound 2 show that the complex to be a two-dimensional polymer, one of Hg atoms has four-coordinate and one of them has seven-coordinate. Three SCN⁻ anions show three different coordination modes with terminal, μ_1,1-bridge and μ_1,3-bridge fashions. The structural studies of compound 3 show the structure may be considered a one-dimensional coordination polymer of mercury(II) consisting of linear chains formed by a bridging 3-bpdb ligand. The thermal stabilities of these compounds were studied by thermal gravimetric (TG) and differential thermal analyses (DTA).     

[Cu4(H2O)4(dmapox)2(btc)]n · 10nH2O: The first two-dimensional polymeric copper(II) complex with bridging μ-trans-oxamidate and μ4-1,2,4,5-benzentetracarboxylato ligands: Synthesis, crystal structure and DNA binding studies

A two-dimensional copper(II) polymer with formula of [Cu₄(H₂O)₄(dmapox)₂(btc)]_n · 10nH₂O, where dmapox is the dianion of N,N′-bis[3-(dimethylamino)propyl]oxamide and btc is the tetra-anion of 1,2,4,5-benzenetetracarboxylic acid, was synthesized and characterized by elemental analysis, conductivity measurement, IR and electronic spectral studies. The crystal structure of the complex has been determined by X-ray single-crystal diffraction. The structure consists of crystallized water molecules and neutral two-dimensional copper(II) coordination polymeric networks constructed both by the bis-tridentate μ-trans-dmapox and tetra-monodentate μ₄-btc bridging ligands. Each btc ligand links four trans-dmapox-bridged binuclear copper(II) building blocks [Cu₂(H₂O)₂(trans-dmapox)]²⁺ and each binuclear copper(II) building block attaches to two btc ligands forming an infinite 2D layer which consists of 4+4 grids with dimensions of 13.563(5) × 15.616(5) Å. The environment around the copper(II) atom can be described as a distorted square-pyramid and the Cu?Cu separations through μ-trans-dmapox and μ₄-btc bridging ligands are 5.225 Å (Cu1-Cu1ⁱ), 5.270 Å (Cu2-Cu2ⁱⁱ), 6.115 Å (Cu1-Cu2), 9.047 Å (Cu1-Cu2ⁱⁱⁱ) and 10.968 Å (Cu1-Cu1ⁱⁱⁱ), respectively. Abundant hydrogen bonds among the crystallized, the coordinated water molecules, and the uncoordinated carboxyl oxygen atoms cross-link the two-dimensional layers into an overall three-dimensional channel-like framework. The interaction of the copper(II) polymer with calf thymus DNA (CT-DNA) has been investigated by using absorption, emission spectral and electrochemical techniques. The results indicate that the copper(II) polymer interacts with DNA strongly (K_b = 4.8 × 10⁵ M⁻¹ and K_sv = 1.1 × 10⁴) and the interaction mode between the copper(II) polymer and DNA may be the groove binding. To the best of our knowledge, this is the first report about the crystal structure and DNA-binding studies of a two-dimensional copper(II) polymer bridged both by the trans-oxamidate and btc ligands.     

A 2-D polymer assembled by cubane-like clusters [Tb4(OH)4(phen)3(H2O)3] and 3-sulfobenzoate

A coordination polymer {[Tb₄(3-SBA)₄(OH)₄(phen)₃(H₂O)₃] · 7H₂O}_n (3-SBA = 3-sulfobenzoate, phen = 1,10-phenanthroline) was synthesized and structurally characterized. The complex contains cubane-like clusters, [Tb₄(μ₃-OH)₄(phen)₃(H₂O)₃]⁸⁺, which are further linked through 3-SBA ligands to form a 2-D grid-like network structure with topology of (3³, 4⁴, 5³). The complex exhibits strong photoluminescence of the Tb³⁺ ion.     

5-Aryl-1-ferrocenylpenta-1,4-dien-3-ones: Synthesis, structures, electrochemistry and third-order nonlinear optical properties

A simple method of synthesis of 5-aryl-1-ferrocenylpenta-1,4-dien-3-ones 5a-e is described. It consists of the condensation of 3-ferrocenylmethylidenepentane-2,4-dione with arenecarboxaldehydes in the presence of an aqueous alkali. Electrochemical and optical properties of the obtained ferrocenyl-containing dienones were studied. It was found that a reversible electron transfer Fc/Fc⁺ takes place in all compounds. In addition, a particular redox behavior of the pyridine moiety Py⁻/Py was detected in the molecule trans-/trans-1-ferrocenyl-5-p-pyridylpenta-1,4-diene-3-one 5c. The cubic nonlinear behavior of the synthesized compounds was tested in solid state at the wavelength range of 1100-1800 nm (telecommunications window). The third-order nonlinear susceptibility χ⁽³⁾(−3ω, ω, ω, ω), measured for polymer films doped with 30 wt.% of aryl(ferrocenyl)penta-1,4-dien-3-ones, was in the range of 1 and 2 × 10⁻¹² esu. Compounds 5a, 5b, 5d and 5e showed, within the experimental error, very similar values for χ⁽³⁾, which means that the phenyl (compound 5a), the p-methoxyphenyl (p-anisyl) (compound 5b), the ferrocenyl (compound 5d), and the p-fluorophenyl (compound 5e) groups give similar behavior for the third-order nonlinearities independently of the electronic effects of these substituents. On the other hand, the nonlinearities were partially enhanced by three-photon resonance.     

A tetracopper(II) complex with N,N′-bis(picolinoyl)hydrazine

Synthesis, physical properties and X-ray structure of a hydrated tetranuclear copper(II) complex [Cu₄(μ-diph)₂(μ-H₂O)₂(O₂CCH₃)₄(H₂O)₂]·4H₂O with N,N′-bis(picolinoyl)hydrazine (H₂diph) are reported. The centrosymmetric complex has two types of copper(II) centres with distorted square-pyramidal N₂O₃ coordination spheres. The dinucleating trans planar diph²⁻ ligands are parallel to each other and act as N₂O-donor to one metal centre and N₂-donor to the other metal centre. The complex has a rectangular {Cu₄(μ-N-N)₂(μ-OH₂)₂} core with Cu···Cu distances as 4.834(1) and 3.762(1) Å. Solid state as well as solution electronic spectra show several transitions in the wavelength range 700-280 nm. The room temperature (298 K) solid state magnetic moment is 3.55 μ_B. The powder EPR spectra at 298 and 130 K are very similar and axial (g_∥ = 2.25 and g_⊥ = 2.08) in character.     

Effects of steric/basic properties of Lewis bases on the degree of aggregation of zinc(II) pivalate complexes

A triangular [Zn₃(μ₃-OH)(OC(O)^tBu)(μ₂-κ¹O:κ¹O′-O₂C^tBu)₄(3,5-lutidine)₃] (1), a paddlewheel based dinuclear [Zn(μ₂-κ¹O:κ¹O′-O₂C^tBu)₂L]₂ [L = 2,4-lutidine (2), 3,4-lutidine (3), and 2,3-lutidine (4)] and an hourglass based linear trinuclear [Zn₃(μ₂-κ¹O:κ¹O′-O₂C^tBu)₆(pyridine)₂] (5) complexes were synthesized to understand the role of subtle steric/basic properties of Lewis bases on the degree of aggregation of the products. The mononuclear Zn(OC(O)^tBu)₂·2H₂O was also prepared in order to probe the origin of the μ₃-OH moiety in complex 1. Complexes 1-5 and Zn(OC(O)^tBu)₂·2H₂O were characterized by microanalytical, IR, TGA/DTA, solution (¹H and ¹³C) NMR, solid-state cross-polarization magic angle spinning (CP-MAS) ¹³C NMR, mass spectral data and single crystal X-ray diffraction data. Complex 1 represents the first example of a discrete trinuclear zinc(II) carboxylate complex that contains a [Zn₃(μ₃-OH)]⁵⁺ core with zinc atoms in three distinct geometries namely a distorted tetrahedral, trigonal bipyramidal, and octahedral. A plausible mechanism for the formation of complexes 1-5 was explained with the aid of point zero charge (pzc) model.     

Influence of Pt and Pd coordination on the equilibrium of 2,2′-dipyridylketone (dpk) with its hydrated gem-diol form (dpk·H2O)

2,2′-Dipyridylketone (dpk), when acting as a chelating ligand for Pd^II or Pt^II, is in slow equilibrium with its corresponding gem-diol form (dpk·H₂O). In D₂O, equilibrium constants K = (dpk·H₂O)/(dpk) change from ca. 0.04 for the free ligand to ca. 3 in the corresponding complexes with cis-[Pt(H₂O)₂]²⁺. In solution, species of both ligands can be identified and differentiated by ¹H NMR spectroscopy, and in the trinuclear μ-OH bridged Pt^II complex [Pt₃(μ-OH)₃(dpk·H₂O)₂(dpk)](NO₃)₃·4.5H₂O (4), both types of ligands are present simultaneously in a ratio of (dpk·H₂O):(dpk) = 2. As demonstrated with a series of Pd^II complexes containing dpk·H₂O and dpk ligands, a straightforward differentiation is possible when DMSO-d₆ is used as solvent, because then also the OH protons of dpk·H₂O are observable. It is also shown that monocrystalline [PdCl₂(dpk·H₂O)] (1), when dissolved in DMSO-d₆, partially converts, with loss of H₂O, to [PdCl₂(dpk)].     

Synthesis and structural characterization of trans-[Mo2(H2DMepyF)2(CH3CN)4](BF4)6 (HDMepyF=N,N-di(6-methyl-2-pyridyl)formamidine)

Reaction of Mo₂(O₂CCH₃)₂(DMepyF)₂ (HDMepyF=N,N^′-di(6-methyl-2-pyridyl)formamidine) with HBF₄ in CH₂Cl₂/CH₃CN afforded the complex trans-[Mo₂(H₂DMepyF)₂(CH₃CN)₄](BF₄)₆ (1), which crystallized in two forms, trans-[Mo₂(H₂DMepyF)₂(CH₃CN)₄](ax-CH₃CN)₂(BF ₄)₆ · 2CH₃CN (1a), and trans- [Mo₂(H₂DMepyF)₂(CH₃CN)₄](ax-BF₄) ₂(BF₄)₄ · 2CH₃CN (1b). The molecular structures of complexes (1) consist of two quadruply bonded molybdenum atoms, which are spanned by two trans-bridging formamidinate ligands and coordinated by four trans-CH₃CN. Each H₂DMepyF⁺ ligand adopts an s-cis,s-cis- conformation. The difference between 1a and 1b is that complex 1a contains two CH₃CN molecules as axial ligands, while 1b contains two BF₄⁻ anions as axial ligands. Complex 1 is the first dimolybdenum complex containing a pair of trans bridging ligands and two pairs of trans-CH₃CN ligands.     

Effects of steric constraint on chromium(III) complexes of tetraazamacrocycles, 4: Comparison of the trans-difluoro-complexes of tet a, 1,4-C2-cyclam, and 1,11-C3-cyclam

The synthesis and characterization of the trans-difluorochromium(III) complexes of the constrained macrocyclic ligands 1,4-C₂-cyclam = 1,4,8,11-tetraazabicyclo[10.2.2]hexadecane and 1,11-C₃-cyclam = 1,4,8,11-tetraazabicyclo[9.3.3]heptadecane is reported. Only trans complexes are formed, and the structures of both trans-[Cr(1,4-C₂-cyclam)F₂]ClO₄ and trans-[Cr(1,11-C₃-cyclam)F₂]ClO₄ are presented. The photochemical and photophysical behavior of the 1,4-C₂-cyclam and 1,11-C₃-cyclam complexes is compared with that of the corresponding tet a (C-meso-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) complex. The constraint imposed by the additional bridging groups of 1,4-C₂-cyclam and 1,11-C₃-cyclam distorts the complexes away from both octahedral symmetry and centrosymmetry, as evidenced by the bond angles that deviate from ideal 90° and 180° values and by a significant distortion of the Cr(N₄) plane. This reduction in symmetry correlates with a monotonic increase in the extinction coefficients in going from the tet a to the 1,11-C₃-cyclam, to the 1,4-C₂-cyclam complex. These three complexes also exhibit large variations in their aqueous room-temperature excited state behavior; namely, the lifetimes of the ²T_1g (O_h) excited states are 30, 60, and 1.0 μs for the tet a, 1,11-C₃-cyclam, and 1,4-C₂-cyclam complexes, respectively. Studies of the excited-state lifetime of these complexes in acidified H₂O/dimethyl sulfoxide over the temperature range between −30 and +95 °C suggest that the 1,4-C₂-cyclam complex accesses a temperature-dependent relaxation mechanism at significantly lower temperatures than do the tet a or 1,11-C₃-cyclam complexes. The emission behavior of these complexes is also solvent-dependent, consistent with established theories that the degree of splitting of the emitting ²T_1g (O_h) state varies with the hydroxylic nature of the solvent.     

Synthesis of trans-1,4-cyclohexanedisulfonic acid and its zinc salt - A belt-like metal-organic coordination polymer with tetrahedrally and octahedrally coordinated zinc ions

Diastereomerically pure trans-1,4-cyclohexanedisulfonic acid H₂CDS was prepared in three steps from 1,4-cyclohexanediol (cis/trans-mixture) as a new linker molecule for metal-organic coordination polymers. The crystalline zinc salt contained two molecules DMF per formular unit. Infinite polymeric belts were observed in the solid state structure of [Zn(CDS)(dmf)₂]. These flat belts were formed by connecting two chains of Zn(dmf)-CDS-polymers bearing tetrahedrally coordinated Zn²⁺ ions in one chain and octahedrally coordinated Zn²⁺ centers in the second. Thermal analysis of this polymer revealed its stability up to 400 °C, above which it decomposed cleanly under formation of crystalline ZnO.     

A convenient synthesis of isocyclam and [16]aneN4 and the photophysics of their dicyanochromium(III) complexes

The syntheses of the tetraazamacrocyclic ligands 1,4,7,11-tetraazacyclotetradecane (isocyclam) and 1,5,9,13-tetraazacyclohexadecane ([16]aneN₄) in two steps starting from the corresponding tetraamine and diethylmalonate is reported. The trans-dicyanochromium(III) complexes, trans-[Cr(isocyclam)(CN)₂]PF₆ and trans-[Cr([16]aneN₄)(CN)₂]PF₆ have also been prepared. Both are ²E_g emitters with 0-0 band emission wavelengths at 721.2 and 704.8 nm, respectively. The isocyclam complex has a room temperature excited state lifetime of 147 μs in aqueous solution which increases to 215 μs upon macrocyclic N-H deuteration, whereas the corresponding lifetime of the [16]aneN₄ complex is 25 μs and is unaffected by macrocyclic N-H deuteration. The implications of the temperature dependence of the excited state lifetimes are also presented.     

Two three-dimensional metal-organic frameworks constructed by multiple building blocks of benzenetricarboxylate and bis(imidazole) ligands

Two novel metal-organic frameworks [Zn₃(BTC)₂(bbi)₃]_n (1) (H₃BTC = 1,3,5-benzenetricarboxylate, bbi = 1,1′-(1,4-butanediyl)bis(imidazole)) and{[Zn₃(BTC)₂(bix)₃ · 2.5H₂O]}_n (2) (bix = 1,4-bis(imidazole-1-ylmethyl)benzene) have been hydrothermally prepared and characterized. Analysis of the structure of 1 displays a 3D framework exhibiting a threefold interpenetration net of identical Zn_1.5(BTC)(bbi)_1.5 single frameworks. In the structure of 2, BTC³⁻ and bix build up infinite tubes extending to a 3D non-interpenetrated porous framework. Moderate fluorescent emissions in the solid state at room temperature were observed in both the compounds.