Substituent Dependence on Series of Cationic Gyroidal MOFs in utc-c Topology with High CO2 Affinity and Ultrahigh Anionic Dye Adsorption Capacity.

A substituent decorating strategy for modification of the functional cavity is of great importance in the design of metal-organic frameworks (MOFs). Herein, three new isostructural cationic MOFs, [Cu3(Xpip)2]·NO3·nH2O (Xpip stands for X-substituted phenylimidazophenanthroline, where X = adm (SCNU-2), f (SCNU-3), and none for SCNU-4), have been successfully synthesized and shown gyroidal utc-c topology and large pore sizes which can be adjusted by different substituents (-N(CH3)2, -F, and -H). Interestingly, the differences of the substituents (sizes and proton donor/acceptor) show essential effects on the adsorption abilities of carbon dioxide and dyes, where SCNU-4 exhibits the highest CO2 affinity and the biggest adsorption capacity for anionic dyes Fluorescein Sodium, and SCNU-3 adsorbs the largest amount (1503.6 mg/g) of Acid Fuchsin to date for the reported porous materials. The detailed studies in adsorption kinetics, adsorption isotherms, and theoretical calculation of the binding energies between the structures and dye molecules confirm that the electric properties of the frameworks (cationic) and substituents directed to the pore surface are two important factors dramatically affecting the selective dye adsorption.

Recent advances in structures and applications of coordination polymers based on cyclohexanepolycarboxylate ligands.

Coordination polymers (CPs) are emerging crystalline materials constructed from metal entities and organic ligands through coordination bonds, containing infinite coordination units in one, two, or three dimensions. Here an overview is given of recent structural research based on seven cyclohexanepolycarboxylates (CHPCs), namely cyclohexanecarboxylate, 1,x-cyclohexanedicarboxylate (x = 2, 3, or 4), 1,3,5-cyclohexanetricarboxylate, 1,2,4,5-cyclohexanetetracarboxylate and 1,2,3,4,5,6-cyclohexanehexacarboxylate, showing the effects of the conformation transformation and auxiliary ligands on the dimensionality and the geometric topology of the assemblies generated. The applications of these CPs as platforms for molecular adsorption, luminescent sensing, magnetism, and catalysis are also briefly discussed.

A Rare 2D Framework Cu(atz)2 with Ferrimagnetic and High Proton Conductivity.

Materials combining proton conductivity and magnetism have attracted great attention in recent years due to their intriguing application in sensors and fuel cells. Herein a two-dimensional metal-organic framework, [Cu(atz)2 (H2 O)2 ]⋅H2 O (1) (Hatz=5-aminotetrazole), has been obtained in a green synthesis method. The single-crystal structure revealed that the atz- ligands as linkers coordinate with copper ions to sql networks, between which water molecules are immobilized through hydrogen bonds. The resulting complex 1 exhibits a high proton conductivity of 1.11×10-4 and 6.19×10-4  S cm-1 at room temperature and 333 K, respectively, under 98% RH with an activation energy of 0.56 eV. Upon dehydration, the proton conductivity of 1_dg drops by an order of magnitude. Furthermore, the magnetic behavior changes from long-range ferrimagnetic ordering of 1 to canted antiferromagnetic behaviour of 1_dg.

A Gyroidal MOF with Unprecedented Interpenetrating utc-c Network Exhibiting Exceptional Thermal Stability and Ultrahigh CO2 Affinity.

A zeolite-like gyroidal MOF (denoted as SCNU-1) constructed with Cu ions and 4-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenol has a featured interpenetrating uninodal utc-c network which is for the first time found in the real structure. Moreover, SCNU-1 exhibits high thermal (>773 K), solvent, and acid/base stabilities; the largest CO2 affinity, 90 kJ/mol, among the MOFs functionalized with an aromatic hydroxyl group; and excellent CO2/N2 selectivity.

Single-crystal-to-single-crystal transformation from 1 D staggered-sculls chains to 3 D NbO-type metal-organic framework through [2+2] photodimerization.

A new approach to synthesize 3D structures through a [2+2] photodimerization process has been carried out by transforming two isostructures of 1D staggered-sculls chains [M(1,2-chdc)(bpe)(2)(H(2)O)(2)]⋅H(2)O (M = Zn, Mn) into 3D NbO-type metal-organic frameworks through UV irradiation in single-crystal-to-single-crystal mode. (see figure; bpe = trans-1,2-(bis(4-pyridyl)ethene, chdc =cyclohexanedicarboxylate).

Two novel Dy8 and Dy11 clusters with cubane [Dy4(µ3-OH)4]8+ units exhibiting slow magnetic relaxation behaviour.

Two unique octa- and hendeca-nuclear dysprosium(III) clusters incorporating [Dy(4)(µ(3)-OH)(4)](8+) cubane units have been synthesized with the 1,10-phenanthroline-2,9-dicarbaldehyde dioxime (H(2)phendox) ligand and DyCl(3)·6H(2)O or Dy(OAc)(3)·4H(2)O. They are [Dy(8)(OH)(8)(phendox)(6)(H(2)O)(8)]Cl(2)(OH)(2)·18H(2)O·18MeOH (1) and [Dy(11)(OH)(11)(phendox)(6)(phenda)(3)(OAc)(3)](OH)·40H(2)O·7MeOH (2). Adjacent Dy(8) in 1 or Dy(11) in 2 motifs are packed by off-set π-π interactions of the aromatic rings on phendox(2-) to generate a 3D supramolecular architecture in the honeycomb topology and with 1D or 3D channels along the c-axis. Adsorption research shows that complex 1 has selective adsorption ability for H(2)O over small gas molecules (H(2), N(2), CO(2)). Complex 2 is stable upon the removal of guest molecules and the desolvated compound absorbed a considerable amount of CO(2). Furthermore, the oximes underwent hydrolysis to carboxylic acid and the resulting 1,10-phenanthroline-2,9-dicarboxylate link the dysprosium atoms to form a hendecanuclear cluster of 2. Magnetic studies reveal that both clusters exhibit slow magnetic relaxation behavior, expanding upon the recent reports of the pure 4f type single-molecule magnets (SMMs).

Solvochromic and photodimerization behaviour of 1D coordination polymer via single-crystal-to-single-crystal transformation.

The coordination polymer [Zn(2)(1,2-bda)(2)(bpe)]·MeOH, which exhibits solvochromic effects upon reversible linear alcohol removal and adsorption, can be turned into [Zn(2)(1,2-bda)(2)(tpcb)(0.5)] in two-step SCSC transformations.

Two new 1,2,4,5-cyclohexanetetracarboxylate-bridged frameworks with metal hydroxide subunits. Synthesis, structures, magnetism and adsorption.

The hydrothermal synthesis, X-ray crystal structures and thermal and magnetic properties of a layered coordination polymer, [Ni(3.9)Mn(1.1)(µ(3)-OH)(2)(L(I))(2)(H(2)O)(10)]·2H(2)O (1) (L(I) = 1e,2a,4a,5e-cyclohexanetetracarboxylate), and a porous 3D coordination polymer, [Ni(4)(µ(2)-OH)(2)(µ(6)-H(2)L(IV))(2)(pymc)(4,4'-bpy)(H(2)O)(2)](OH)·9H(2)O (2) (pymc = 2-pyrimidinecarboxylate, 4,4'-bpy = 4,4'-bipyridine, L(IV) = 1e,2e,4e,5e-cyclohexanetetracarboxylate), are reported in this paper. The structure of 1 has packed separated layers, each layer being formed of M(3)(µ(3)-OH)(2) chains bridged by M(L(I))(2)via hydrogen bonds. The magnetic properties are characterized by Néel transitions to fully compensated antiferromagnets at 2.9 K and show that 1 is a metamagnet resulting from the ferrimagnetic M(3)(µ(3)-OH)(2) chains and other two metal atoms. Complex 2 is a 3D microporous coordination framework with 2D channels. The conformation of the 1,2,4,5-cyclohexanetetracarboxylate ligands (H(4)L) of complex 2 changes from L(I) (e,a,a,e) to L(IV) (e,e,e,e). The magnetic measurement indicates spin-canted antiferromagnetic behaviour, and the adsorption measurements show that 2 can selectively adsorb CO(2) gas over N(2) gas.

Chiral transition metal clusters from two enantiomeric schiff base ligands. Synthesis, structures, CD spectra and magnetic properties.

Two enantiomeric Schiff base ligands R-/S-H2L in situ generated from the condensation of o-vanillin with R- or S-2-phenylglycinol were applied to assemble chiral multinuclear transition metal magnetic clusters for the first time. Four new enantiomerically pure chiral clusters, [NaMn4(3-O)(N3)1.75Br0.25(R-L)3(MeOH)2(H2O)2][NaMn4(mu3-O)(N3)2(R-L)3(MeOH)2(H2O)2]Br4 (1R), [NaMn4(mu3-O)(N3)1.75Br0.25(S-L)3(MeOH)2(H2O)2][NaMn4(mu3-O)(N3)2(S-L)3(MeOH)2(H2O)2]Br4 (1S), [Cu6(R-L)2(R-HL)2(N3)5(MeOH)]NO3.2MeOH.H2O (2R) and [Cu6(S-L)2(S-HL)2(N3)5(MeOH)]NO3.2MeOH.H2O (2S), have been synthesized and characterized by single crystal X-ray crystallography and CD spectroscopy. Three Mn(III) in the MnIIMnIII3 clusters of 1R and 1S are joined together through the 3-O bridge to form an oxo-centered Mn3O unit. Three L2- link four manganese atoms via the mu2-O,N,O-bridging manner into a MnIIMnIII3 cluster in a distorted tetrahedral geometry. Enantiomeric 2S and 2R are hexanuclear copper(II) clusters composed of a cubane-like Cu4L4 part with a dinuclear Cu2(N3)2 unit capped on one of the faces of the Cu4L4 cubane via the mu1,1-azide and phenolate bridges from the chiral ligands. Magnetic analysis reveals intracluster antiferromagnetic interaction between adjacent manganese ions in chiral oxo-centered MnIIMnIII3 magnetic clusters for 1R and 1S, and dominating antiferromagnetic over weak ferromagnetic interactions in Cu6 clusters in 2R and 2S.

Synthesis, structures, adsorption behaviour and magnetic properties of a new family of polynuclear iron clusters.

Solvothermal reactions of 1,10-phenanthroline-2,9-dicarbaldehyde dioxime (H(2)phendox) with FeCl(3)·6H(2)O or FeBr(3) under solvothermal conditions yielded two trinuclear iron(III) clusters [Fe(III)(3)(mu(3)-O)(phendox)(3)]X·14H(2)O (X = Cl 1·14H(2)O, Br 2·14H(2)O) and three hexanuclear iron(III) and iron(II) clusters, [Fe(III)(6)(mu(4)-O)(2)(MeO)(6)X(4)(phendox)(2)]·MeOH (X = Cl , Br 4) and (H(3)O)[Fe(II)(6)(mu(6)-Cl)(phenda)(6)]·6H(2)O (5·6H(2)O). The phendox(2-) ligand is very useful in constructing magnetically active and stable high-nuclearity metal clusters in that the phenanthroline rings and the oxime nitrogen atoms grasp the metal ions tightly while the two oxygen atoms on the oximates can link other metal centres in the shortest pairwise magnetic exchange pathway. Adjacent Fe(3)(mu(3)-O)(phendox)(3)(+) motifs in 1 and 2 are packed by off-set pi-pi interactions of the aromatic rings on phendox(2-) to generate a 3D supramolecular architecture in the honeycomb topology and with 1D hexagonal channels in the dimension of 13 x 13 Å along the c-axis. 2 is stable upon the removal of guest molecules and the desolvated compound absorbed considerable amount of N(2), CO(2) and H(2). 3 and 4 are isostructural. Two mu(4)-O(2-) and two phendox(2-) units link four metal atoms into a coplanar butterfly-shaped unit with the mu(4)-O(2-) slightly above and below the plane (+/-0.264 Å). The other two Fe(III) ions are capped on the alternate planes via the three bridging mu(2)-methoxides and accordingly form an unprecedented hexanuclear Fe(III) cluster. Furthermore, the oximes underwent hydrolysis to yield carboxylate groups and the resulted 1,10-phenanthroline-2,9-dicarboxylate link the iron atoms to form a hexanuclear cluster of 5. Magnetic studies show that the antiferromagnetic interactions are present in the Fe(3)O core of 2 and in the (mu(6)-Cl)Fe(6)(mu-O)(12) core of 5.

Reactivity of 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole, structures and magnetic properties of polynuclear and polymeric Mn(II), Cu(II) and Cd(II) complexes.

Five new complexes were obtained from solution or hydrothermal reactions of M(OAc)(2) (M = Mn, Cu and Cd) or CuCl(2) with 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (abpt) and NaN(3) or 1,3,5-benzenetricarboxylic acid (btcH(3)) in different molar ratios. Structural analysis reveals that Cd(abpt) units in [Cd(abpt)(mu(1,1)-N(3))(2)](n) (1) are bridged by double mu(1,1) end-on (EO) azides into 1D zigzag coordination chains. Similar structural motifs, i.e. the chelation of abpt to the metal center and the double bridges of EO azides, are found in [Mn(4)(abpt)(4)(mu(1,1)-N(3))(8)(H(2)O)(2)] (2). The terminal aqua molecules and the monodentate N(3)(-) groups lead to the formation of a tetranuclear complex rather than a polymeric compound. The abpt underwent deamination in the presence of copper ions during the process of coordination and became 3,5-bis(pyridin-2-yl)-1,2,4-triazolate (bpt-H) in 3-5. [Cu(4)(bpt-H)(4)(N(3))(4)].4.5H(2)O (3) is a neutral tetranuclear grid-like complex, in which the azides act as monodentate ligands. A similar [Cu(4)(bpt-H)(4)](4+) grid-like unit was found in [Cu(4)(bpt-H)(4)(mu-btcH)Cl(2)].2H(2)O (4) and a pair of symmetry-related copper atoms are bridged by the mu-btcH(2)(-) coligand in a butterfly-shaped structure. In [Cu(2)(bpt-H)(mu(6)-btc)(H(2)O)](n) (5), the tetranuclear {Cu(4)(mu-bpt-H)(2)(mu(3)-carboxylate)(2)}(4+) units are bridged by mu(6)-btc(3-) ligands in a 2D step-like layer structure. Temperature-dependent magnetic susceptibility measurements reveal that the double mu(1,1)-N(3)(-) bridges in 2 transmit the ferromagnetic interactions between Mn(2+) centers (J(1) = J(2) = +3.09(4) cm(-1), g(Mn(II)) = 2.02(1)), and the mu-(bpt-H)(-) bridges transmit moderate antiferromagnetic interactions in both 3 (J = -12.78(13) cm(-1)) and 4 (J(1) = -14.96(11) cm(-1)). In 4 the antiferromagnetic coupling via the mu-btcH(2-) bridge was found as the second coupling pathway (J(2) = -9.48(7) cm(-1)). The coexistence of ferromagnetic and antiferromagnetic coupling between four Cu(2+) centers occurs in 5 (J(1) = -0.88(3) cm(-1) and J(2) = +5.01(2) cm(-1)). The magneto-structural relationship for tetranuclear copper pyrazolate/triazolate compounds has been discussed.

Coordination chemistry of conformation-flexible 1,2,3,4,5,6-cyclohexanehexacarboxylate: trapping various conformations in metal-organic frameworks.

To study the conformations of 1,2,3,4,5,6-cyclohexanehexacarboxylic acid (H(6)L), eleven new coordination polymers have been isolated from hydrothermal reactions of different metal salts with 1e,2a,3e,4a,5e,6a-cyclohexanehexacarboxylic acid (3e+3a, H(6)L(I)) and characterized. They are [Cd(12)(mu(6)-L(II))(mu(10)-L(II))(3)(mu-H(2)O)(6)(H(2)O)(6)]16.5 H(2)O (1), Na(12)[Cd(6)(mu(6)-L(II))(mu(6)-L(III))(3)]27 H(2)O (2), [Cd(3)(mu(13)-L(II))(mu-H(2)O)] (3), [Cd(3)(mu(6)-L(III))(2,2'-bpy)(3)(H(2)O)(3)]2 H(2)O (4), [Cd(4)(mu(4)-L(VI))(2)(4,4'-Hbpy)(4)(4,4'-bpy)(2)(H(2)O)(4)]9.5 H(2)O (5), [Cd(2)(mu(6)-L(II))(4,4'-Hbpy)(2)(H(2)O)(10)]5 H(2)O (6), [Cd(3)(mu(11)-L(VI))(H(2)O)(3)] (7), [M(3)(mu(9)-L(II))(H(2)O)(6)] (M=Mn (8), Fe (9), and Ni (10)), and [Ni(4)(OH)(2)(mu(10)-L(II))(4,4'-bpy)(H(2)O)(4)]6 H(2)O (11). Three new conformations of 1,2,3,4,5,6-cyclohexanehexacarboxylate, 6e (L(II)), 4e+2a (L(III)) and 5e+1a (L(VI)), have been derived from the conformational conversions of L(I) and trapped in these complexes by controlling the conditions of the hydrothermal systems. Complexes 1 and 2 have three-dimensional (3D) coordination frameworks with nanoscale cages and are obtained at relatively low temperatures. A quarter of the L(I) ligands undergo a conformational transformation into L(II) while the others are transformed into L(III) in the presence of NaOH in 2, while all of the L(I) are transformed into L(II) in the absence of NaOH in 1. Complex 3 has a 3D condensed coordination framework, which was obtained under similar reaction conditions as 1, but at a higher temperature. The addition of 2,2'-bipyridine (2,2'-bpy) or 4,4'-bipyridine (4,4'-bpy) to the hydrothermal system as an auxiliary ligand also induces the conformational transformation of H(6)L(I). A new L(VI) conformation has been trapped in complexes 4-7 under different conditions. Complex 4 has a 3D microporous supramolecular network constructed from a 2D L(III)-bridged coordination layer structure by pi-pi interactions between the chelating 2,2'-bpy ligands. Complexes 5-7 have different frameworks with L(II)/L(VI) conformations, which were prepared by using different amounts of 4,4'-bpy under similar synthetic conditions. Both 5 and 7 are 3D coordination frameworks involving the L(VI) ligands, while 6 has a 3D microporous supramolecular network constructed from a 2D L(II)-bridged coordination layer structure by interlayer N(4,4'-Hbpy)--HO(L(II)) hydrogen bonds. 3D coordination frameworks 8-11 have been obtained from the H(6)L(I) ligand and the paramagnetic metal ions Mn(II), Fe(II), and Ni(II), and their magnetic properties have been studied. Of particular interest to us is that two copper coordination polymers of the formulae [{Cu(II) (2)(mu(4)-L(II))(H(2)O)(4)}{Cu(I) (2)(4,4'-bpy)(2)}] (12 alpha) and [Cu(II)(Hbtc)(4,4'-bpy)(H(2)O)]3 H(2)O (H(3)btc=1,3,5-benzenetricarboxylic acid) (12 beta) resulted from the same one-pot hydrothermal reaction of Cu(NO(3))(2), H(6)L(I), 4,4'-bpy, and NaOH. The Hbtc(2-) ligand in 12 beta was formed by the in situ decarboxylation of H(6)L(I). The observed decarboxylation of the H(6)L(I) ligand to H(3)btc may serve as a helpful indicator in studying the conformational transformation mechanism between H(6)L(I) and L(II-VI). Trapping various conformations in metal-organic structures may be helpful for the stabilization and separation of various conformations of the H(6)L ligand.

Hydrothermal synthesis, structures, and photoluminescent properties of benzenepentacarboxylate bridged networks incorporating zinc(II)-hydroxide clusters or zinc(II)-carboxylate layers.

The first coordination compounds of partially or wholly deprotonated benzenepentacarboxylic acid (H5L) were synthesized in the presence or absence of auxiliary 2,2'-bipyridyl (2,2'-bpy) and 1,10-phenanthroline (phen) ligands, and their crystal structures and photoluminescent properties were characterized. Their formulas are [Zn6(mu3-OH)2(L)2(H2O)6]n (1), [Zn5(mu3-OH)2(HL)2(2,2'-bpy)2]n (2), [Zn2(HL)(phen)2(H2O)2]n (3), and [Zn5(L)2(phen)4(H2O)3]n.2nH2O (4). Both 1 and 2 are three-dimensional (3D) zinc(II)-hydroxide cluster based coordination frameworks. 1 contains distorted chairlike hexanuclear Zn6(mu3-OH)2 cluster units as secondary building blocks. Each Zn6(mu3-OH)2 unit connects six others through the three-connected nodes of L5- ligands into a 3D rigid and condensed coordination network, whereas in 2, each pentanuclear Zn5(mu3-OH)2 unit connects the other six ones through the three-connected [HL]4- nodes into a 3D network in the simple cubic packing mode. 3 has two-dimensional (2D) Zn(II)-carboxylate supramolecular layers constructed from a one-dimensional (1D) coordination chain structure by hydrogen bonds of the water and mu5-[HL]4- bridges, whereas 4 has 2D coordination layers composed of Zn(II) and mu8-L5- bridges. The adjacent coordination assemblies in 3 and 4 are further extended by hydrogen bonds and pi...pi interactions into 3D supramolecular architectures. 1-4 are photoluminescent active materials, and their photofluorescent properties are closely related to their intrinsic structure arrangements.