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A porous metal-organic framework, Mn(H(3)O)[(Mn(4)Cl)(3)(hmtt)(8)] (POST-65), was prepared by the reaction of 5,5',10,10',15,15'-hexamethyltruxene-2,7,12-tricarboxylic acid (H(3)hmtt) with MnCl(2) under solvothermal conditions. POST-65(Mn) was subjected to post-synthetic modification with Fe, Co, Ni, and Cu according to an ion-exchange method that resulted in the formation of three isomorphous frameworks, POST-65(Co/Ni/Cu), as well as a new framework, POST-65(Fe). The ion-exchanged samples could not be prepared by regular solvothermal reactions. The complete exchange of the metal ions and retention of the framework structure were verified by inductively coupled plasma-atomic emission spectrometry (ICP-AES), powder X-ray diffraction (PXRD), and Brunauer-Emmett-Teller (BET) surface-area analysis. Single-crystal X-ray diffractions studies revealed a single-crystal-to-single-crystal (SCSC)-transformation nature of the ion-exchange process. Hydrogen-sorption and magnetization measurements showed metal-specific properties of POST-65.

The reaction of equimolar amounts of Ni(NO3)2·6H2O, Na2(suc)·6H2O (suc = succinate) and 4,4′-bipyridine (bipy) under different conditions yield the coordination polymers [Ni(suc)(bipy)(H2O)2]n·2nH2O (1) and [Ni(suc)(bipy)(H2O)2]n·nH2O (2). The complexes were characterized by elemental analysis, spectroscopic, thermogravimetric, and magnetic susceptibility measurements. Crystal structures reveal that the metal centers in both complexes are in a distorted octahedral N2O4 coordination sphere assembled by mutually trans pairs of 4,4′-bipyridine, succinate, and water molecules. The helical metal–succinate chains have a right-handed sixfold configuration in 1, with guest water molecules inside the helix, and both right- and left-handed fourfold configurations in 2, with guest water molecules outside the helix. The parallel helical substructures are connected by 4,4′-bipyridine and provide 3D chiral 75.9 and achiral 65.8 networks in 1 and 2, respectively.

For the first time, phase-pure interpenetrated MOF-5 (1) has been synthesized and its gas sorption properties have been investigated. The phase purity of the material was confirmed by both single-crystal and powder X-ray diffraction studies and TGA analysis. A systematic study revealed that controlling the pH of the reaction medium is critical to the synthesis of phase-pure 1, and the optimum apparent pH (pH*) for the formation of 1 is 4.0-4.5. At higher or lower pH*, [Zn(2)(BDC)(2)(DMF)(2)] (2) or [Zn(5)(OH)(4)(BDC)(3)] (3), respectively, was predominantly formed. The pore size distribution obtained from Ar sorption experiments at 87 K showed only one peak, at ~6.7 Å, which is consistent with the average pore size of 1 revealed by single crystal X-ray crystallography. Compared to MOF-5, 1 exhibited higher stability toward heat and moisture. Although its surface area is much smaller than that of MOF-5 due to interpenetration, 1 showed a significantly higher hydrogen capacity (both gravimetric and volumetric) than MOF-5 at 77 K and 1 atm, presumably because of its higher enthalpy of adsorption, which may correlate with its higher volumetric hydrogen uptake compared to MOF-5 at room temperature, up to 100 bar. However, at high pressures and 77 K, where the saturated H(2) uptake mostly depends on the surface area of a porous material, the total hydrogen uptake of 1 is notably lower than that of MOF-5.

The synthesis and physical properties of bis(2-(1H-imidazol-2-yl)-pyridine)copper(II) with chloride, nitrate and perchlorate as counteranions have been described. Microanalysis, magnetic susceptibility, conductivity and various spectroscopic measurements have been used for the characterization of the complexes. The crystal structures of all three complexes have been determined. Intermolecular hydrogen-bonding interactions and the resulting self-assembly patterns for each of the species have been scrutinized. The chloride containing complex crystallizes as a trihydrate, where the metal ion is in a tetragonally elongated cis-N4Cl2 coordination sphere. This complex provides a three-dimensional honeycomb-like structure through N–H⋯Cl, O–H⋯Cl and O–H⋯O hydrogen bonds. In the nitrate containing species, one of the two counteranions coordinates to the metal centre to provide an irregular N4O2 coordination sphere, while the other counteranion, with the help of a lattice water molecule, assembles a ladder-like structure via N–H⋯O and bifurcated O–H⋯O,O hydrogen bonds. A one-dimensional polymeric species has been formed when perchlorate is the counteranion. Here one of the two perchlorates acts as a bridge between the metal centres that are in tetragonally elongated trans-N4O2 coordination spheres. This polymeric chain, together with the second perchlorate and a water molecule, form a ribbon-like structure due to N–H⋯O and O–H⋯O hydrogen bonds.

A series of copper(II) complexes having the formula [Cu( n - R -pyp)X] with the N,N,O-donor Schiff base system 2- N -(picolinylidene)- n - R -phenol ( n - R -Hpyp) (where n = 3, 4, 5 and 6, when R = Me and n = 4 when R = Cl) and halide (X − = Cl − or Br − ) as an ancillary ligand have been synthesized. The complexes are characterized by microanalytical, magnetic and various spectroscopic measurements. They display solvatochromic behavior. Single crystal X-ray structures of all the complexes are determined. In coordinatively unsaturated species such as a square–planar complex, the metal ion can interact with a fifth atom and if this atom is metal bound, dimeric or polymeric aggregate is formed. In the present series of complexes, the metal ions are square–planar and distorted square–pyramidal when there is an intermolecular Cu···X interaction. In addition to this Cu···X interaction, presence of intermolecular weak non-covalent interactions namely O–H···O, C–H···O, C–H···X and π···π are perceived. The supramolecular architectures formed by the molecules of these complexes via these interactions are scrutinized. The observed supramolecular structural motifs can be classified as staircase, ladder, brick-wall and square-grid. Except for R = Cl the analogous chloride and bromide coordinated complexes show similar structural features.

Store it away: Methane adsorption isotherms of Zn2(bdc)2(dabco) (1) are measured up to a pressure of 35 bar. X-ray structure analysis of methane-adsorbed 1 at 90 K reveals that methane molecules occupy three independent sorption sites A, B, and C while interacting with the framework as well as each other through van der Waals interactions. Sorption isotherms of methane in Zn2(bdc)2(dabco) are measured up to a pressure of 35 bar in the temperature range between 198–296 K. The methane sorption measurements at 296 K showed an uptake of 137 cm3 cm−3 at 35 bar. The enthalpy of methane adsorption for Zn2(bdc)2(dabco) estimated by the virial equation is 13.6 kJ mol−1 at zero coverage. X-ray structure analysis of methane-adsorbed Zn2(bdc)2(dabco) by synchrotron radiation at 90 K revealed that methane molecules occupy three independent sorption sites (A, B, and C) with a stoichiometry of Zn2(bdc)2(dabco)⋅6.69CH4, which is consistent with the results of the gas sorption measurements at 198 K. In a cavity, eight symmetry-related methane sorption sites A are located near the {Zn2(CO2)4} paddle-wheel units, while four symmetry-related methane sorption sites B are near the center of the small windows along the a and b axes. Both A and B sites are half-occupied. Methane molecules occupying sites A are not only in van der Waals contact with the paddle-wheel units, but also interact with the phenyl rings of bdc ligands through partial π-HC interactions. Methane molecules in B sites interact with the side of the phenyl rings through van der Waals interaction. The site C, located at the center of the cavity, is a secondary sorption site; methane molecules occupying sites C are in van der Waals contact with those in sites A and B.

Copper(II) complexes having the general formula [Cu(Ln)2] with the N,O-donor reduced Schiff bases N-(2-hydroxy-5-X-benzyl)-(R)-α-methylbenzylamine and N-(2-hydroxy-5-X-benzyl)-(S)-α-methylbenzylamine (X = Cl and Br) (HLn) are described. These chiral complexes crystallize in the noncentrosymmetric P212121 (X = Cl) and P21 (X = Br) space groups. In each case, self-assembly via intermolecular C–H⋯O interaction leads to a supramolecular helical superstructure.

Two ternary copper(II) complexes having the general formula [Cu(pyp)X] with the tridentate Schiff base 2-N-(picolinylidene)phenol (Hpyp) and halide (X- = Cl-, Br-) as the ancillary ligand have been synthesized and characterized. Both complexes exhibit solvatomorphism due to cocrystallization with different solvent molecules. Two cases have been investigated: (i) the dihydrated species [Cu(pyp)Cl]·2H2O (1) and [Cu(pyp)Br]·2H2O (2), isolated by slow evaporation of aqueous methanol solution of the complexes, and (ii) the corresponding monomethanolic forms [Cu(pyp)Cl]·CH3OH (3) and [Cu(pyp)Br]·CH3OH (4), obtained by crystallization of 1 and 2 from dry methanol. To investigate the crystal compositions and packing features, single-crystal X-ray diffraction measurements as well as thermogravimetric and differential scanning calorimetric measurements have been carried out. In the context of structural features, the hydrated forms and also the monomethanolic forms are isomorphic. The dihydrated form shows a zippe...

Reactions of Li2[PdCl4] with N-(aroyl)-N′-(2,4-dimethoxybenzylidene)hydrazines (H2L = (4-R–C6H4)C( O)NHN CH(2,4-(CH3O)2C6H3)) in presence of PPh3 have provided cyclopalladated complexes having the general formula [PdL(PPh3)] (1, 2 and 3 where R = OCH3, CH3 and Cl, respectively) and a coordination complex trans-[Pd(HL)(PPh3)2Cl] (4 where R = NO2). The complexes have been characterized by elemental analysis, infrared, 1H NMR and electronic absorption spectroscopy. X-ray structures of all the complexes have been determined. In 1, 2 and 3, the C,N,O-donor dianionic ligand (L2−) forms two fused five-membered chelate rings at the metal centre. On the other hand, the monoanionic ligand (HL−) acts as deprotonated amide N-donor in 4. The strong electron withdrawing effect of the nitro group on the aroyl fragment is possibly responsible for the monodentate amide N-coordinating behavior of HL− in 4. The orientation of the 4-methoxy group in 1 is different than that in 2 and 3 due to intramolecular C–H⋯π interaction in the last two complexes. The structure of 4 shows an apical C–H⋯Pd interaction involving the azomethine (–CH N–) group of HL−. In the crystal lattice of all the structures, various types of intermolecular non-covalent interactions are present. The self-assembly of the molecules of 1, 2 and 3 leads to two-dimensional networks. The same network observed for 2 and 3 reflects the interchangeability of the chloro and methyl groups due to their similar volumes. In the case of 4, the complex and the water molecules present in the crystal lattice form parallel homo-chiral helices and finally interhelical interactions lead to a three-dimensional network.

The reaction of Mn(OAc)2 · 4H2O and 1-alkyl-2-(arylazo)imidazole [RaaiR′ where R = H (a), Me (b); R′ = Me (1/3/), Et (2/4/)] and NH4NCS in MeOH in a 1:2:2 mole ratio afforded [Mn(RaaiR′)2(NCS)2] (3) and (4) complexes. They were characterized by different physicochemical methods and the structure has been confirmed by single crystal X-ray diffraction study for title compound. One of the primary ligands was also characterised by an X-ray diffraction study.

Ternary copper(II) complexes having the general formula [Cu(bhs)(hc)], with a tridentate Schiff base, N-(benzoyl)-N′-(salicylidine)-hydrazine (H2bhs) and monodentate N-heterocycles (hc=3,5-dimethylpyrazole, pyrazole, imidazole, and pyridine), are described. The complexes were characterized by elemental analysis, spectroscopic and cryomagnetic measurements and X-ray crystallography. Analytical data, infrared and electronic spectral features and molar conductivity values are consistent with the proposed molecular formula and the +2 oxidation state of the metal ion in these complexes. Cryomagnetic and EPR spectral measurements showed weak antiferromagnetic spin-exchange in all four complexes. In each complex, the metal ion is in N2O2 square-plane constituted by the phenolate-O, the imine-N, and the deprotonated amide-O donor bhs2− and the sp2 N-donor neutral heterocycle. In the solid state, the complexes having 3,5-dimethylpyrazole, imidazole, and pyridine as the heterocyclic ligand, exist as centrosymmetric dimeric species due to weak apical coordination of the metal bound phenolate-O. On the other hand, only one of the two molecules present in the asymmetric unit of the complex containing pyrazole forms the centrosymmetric dimeric species due to weak apical coordination of the metal bound amide-O. In the crystal lattice, intermolecular π–π, C–H⋯π, C–H⋯N, O–H⋯N and N–H⋯O interactions involving the complex and the solvent molecules lead to one- and two-dimensional supramolecular structures.

Three ternary copper(II) complexes of general formula [Cu(bhac)(hc)], with a tridentate Schiff base, acetylacetone benzoylhydrazone (H2bhac) and monodentate N-heterocycles (hc=pyrazole, imidazole and pyridine), have been synthesized. Elemental analysis, various forms of spectroscopy (infrared, electronic absorption and EPR), cyclic voltammetry, cryomagnetic measurements and X-ray crystallography were used for the characterization of the complexes. Analytical data, infrared and electronic spectral features and molar conductivity values are consistent with the proposed molecular formulae and the +2 oxidation state of the metal ion in these complexes. In each complex, the enolate-O, the imine-N and the deprotonated amide-O donor tridentate ligand (bhac2−) and the sp2 N donor heterocycle form an O2N2 square-plane around the metal ion. The whole molecule of none of the complexes is perfectly planar because of different orientation of the phenyl ring plane of the tridentate ligand and that of the heterocycle ring plane with respect to the plane containing rest of the molecule. In the solid state, the complexes having the pyrazole and the pyridine as the heterocyclic ligand, exist as centrosymmetric dimeric species due to very weak apical coordination of the metal bound enolate-O. The complex of imidazole has no such apical coordination and exists as a monomer. In the crystal lattice, the molecules of these complexes are involved in a variety of intermolecular non-covalent interactions such as O–H⋯O, N–H⋯O, N–H⋯N, C–H⋯π and π⋯π. Self-assembly via these interactions lead to a one-dimensional arrangement of [Cu(bhac)(Hpyrz)]·C2H5OH, a two-dimensional layered structure of [Cu(bhac)(Himdz)] and a three-dimensional network of [Cu(bhac)(py)]. Cryomagnetic and EPR spectral measurements indicates weak antiferromagnetic spin-exchange in all the three complexes.

Cyclopalladated complexes with the Schiff base N-(benzoyl)-N′-(2,4-dimethoxybenzylidene)hydrazine (H2L, 1) have been described. The reaction of 1 with Li2[PdCl4] in methanol yields the complex [Pd(HL)Cl] (2). [Pd(HL)(CH3CN)Cl] (3) has been prepared by dissolving 2 in acetonitrile. In methanol–acetonitrile mixture, treatment of 2 with two mole equivalents of PPh3 produces [PdL(PPh3)] (4) and that with one mole equivalent of PPh3 produces [Pd(HL)(PPh3)Cl] (5). Crystallization of 2 from dmso-d6 results into isolation of [Pd(HL)((CD3)2SO)Cl] (6). In 2, the monoanionic ligand (HL−) is C,N,O-donor and the Cl-atom is trans to the azomethine N-atom. In 3, 5 and 6, HL− is C,N-donor and the Cl-atom is trans to the metallated C-atom. The remaining fourth coordination site is occupied by the N-atom of CH3CN, the P-atom of PPh3 and the S-atom of (CD3)2SO in 3, 5 and 6, respectively. Thus on dissolution in acetonitrile and dmso and in reaction with stoichiometric PPh3 the incoming ligand imposes a rearrangement of the coordinating atoms on the palladium centre. On the other hand, in presence of excess PPh3 deprotonation of the amide functionality in 2 occurs and the Cl-atom is replaced by the P-atom of PPh3 to form 4. Here the dianionic ligand (L2−) remains C,N,O-donor as in 2. The compounds have been characterized with the help of elemental analysis (C, H, N), infrared, 1H NMR and electronic absorption spectroscopy. Molecular structures of 3, 4, and 6 have been determined by X-ray crystallography.

A mixed-ligand copper(II) complex, [Cu(bhac)(Hdmpz)], with a tridentate Schiff base, acetylacetone benzoylhydrazone (H2bhac) and a monodentate heterocycle, 3,5-dimethylpyrazole (Hdmpz), has been synthesized and characterized by analytical, infrared and electronic absorption spectroscopy, and cyclic voltammetry. The molecular structure of the complex has been determined by X-ray crystallography. The metal ion is coordinated to the enolate-O, the imine-N and the deprotonated amide-O centres of the deprotonated Schiff base (bhac2−) and to the sp2 N atom of Hdmpz. The coordination geometry around the metal centre is square-planar. There is no displacement of the metal centre from the N2O2 square plane. The whole molecule is essentially planar, barring a small variation in the orientation of the Hdmpz plane with respect to the {Cu(bhac)} plane. In the solid state, two types of π-π interactions on two sides of [Cu(bhac)(Hdmpz)] molecule lead to a one-dimensional arrangement of the complex with sequential short [3.5952(8) A] and long ([5.5960(12) A] Cu⋯Cu distances. Solid state as well as frozen solution EPR spectral measurements reveal an antiferromagnetically coupled dicopper(II) system and indicate a magnetic exchange interaction mediated by π-π interactions. Magnetic susceptibility data in the temperature range of 10–300 K are consistent with this observation. The magnitude of the coupling constant J, obtained by least-squares fitting of the data using the Bleany–Bowers expression, is −6.0(1) cm−1.

In the light of growing demand for chiral purity in biological and chemical processes, the synthesis of chiral metal-organic porous materials (CMOPMs) have become immensely important because of their potential applications in chiral separation and asymmetric catalysis. In this chapter, the synthetic strategies for CMOPMs are discussed briefly keeping the focus on their applications. Two distinct approaches have been taken to synthesize a wide variety of chiral structures with different topologies and accessible cavities. Several CMOPMs have shown catalytic activity and enantioselectivity toward a number of chemical transformations. On many occasions, the chiral pores of the MOPMs have been utilized in order to achieve separation of enantiomers from racemates. Recent applications of homochiral MOPMs in heterogeneous asymmetric catalysis and chiral separations are also presented here.

The postsynthetic modification strategy is adopted to demonstrate for the first time the syntheses of catalytically active chiral MOPMs from a preassambled achiral framework, MIL-101, by attaching l-proline-derived chiral catalytic units to the open metal coordination sites of the host framework. Various characterization techniques (including PXRD, TGA, IR, and N2 absorption measurements) indicated that the chiral units are successfully incorporated into MIL-101, keeping the parent framework intact. The new chiral MOPMs show remarkable catalytic activities in asymmetric aldol reactions (yield up to 90% and ee up to 80%). It is interesting to note that these heterogeneous catalysts show much higher enantioselectivity than the corresponding chiral catalytic units as homogeneous catalysts. This study demonstrates a simple and efficient route for the generation of catalytically active chiral MOPMs. A variety of chiral catalytic units can be, in principle, incorporated into chemically robust achiral MOPMs with...

In the light of growing demand for chiral purity in biological and chemical processes, the synthesis of chiral metal-organic porous materials (CMOPMs) have become immensely important because of their potential applications in chiral separation and asymmetric catalysis. In this chapter, the synthetic strategies for CMOPMs are discussed briefly keeping the focus on their applications. Two distinct approaches have been taken to synthesize a wide variety of chiral structures with different topologies and accessible cavities. Several CMOPMs have shown catalytic activity and enantioselectivity toward a number of chemical transformations. On many occasions, the chiral pores of the MOPMs have been utilized in order to achieve separation of enantiomers from racemates. Recent applications of homochiral MOPMs in heterogeneous, asymmetric catalysis and chiral separations are also presented here.

In methanol, the reaction of Cu(ClO(4))(2).6H(2)O and a sterically constrained piperazine imine phenol ligand (H(2)L), in the presence of NEt(3), affords a novel tetranuclear copper(II) complex of formula [Cu(II)(4)(mu(3)-L)(2)(mu-OH)(2)(H(2)O)(2)](ClO(4))(2).H(2)O (1). The X-ray structure of this complex shows an elongated Cu(4) quasi-tetrahedron coordinated to two hexadentate chair-(e,a)-mu(3)-piperazine bridging ligands. Variable-temperature magnetic studies show an S(t) = 0 spin ground state resulting from antiferromagnetic interactions between Cu(II) ions within the complex.

The postsynthetic modification strategy is adopted to demonstrate for the first time the syntheses of catalytically active chiral MOPMs from a preassambled achiral framework, MIL-101, by attaching L-proline-derived chiral catalytic units to the open metal coordination sites of the host framework. Various characterization techniques (including PXRD, TGA, IR, and N(2) absorption measurements) indicated that the chiral units are successfully incorporated into MIL-101, keeping the parent framework intact. The new chiral MOPMs show remarkable catalytic activities in asymmetric aldol reactions (yield up to 90% and ee up to 80%). It is interesting to note that these heterogeneous catalysts show much higher enantioselectivity than the corresponding chiral catalytic units as homogeneous catalysts. This study demonstrates a simple and efficient route for the generation of catalytically active chiral MOPMs. A variety of chiral catalytic units can be, in principle, incorporated into chemically robust achiral MOPMs with large pores by postmodification and the resulting chiral MOPMs may find useful applications in catalytic asymmetric transformations.

We report for the first time the complete and reversible exchange of metal ions constituting a robust microporous framework while maintaining not only the structural integrity of the framework but also single crystallinity. Solvothermal reaction of Cd(NO(3))(2) .4H(2)O with H(3)hett in DMF produced a new crystalline MOF 1 having a cubic network with 3D channels. The basic building unit of the framework 1 is an octahedron where the square planar tetrametallic SBUs ({Cd(4)O}(6+)) and tricarboxylate linkers (hett(3-)) occupy the vertices and triangular faces of the octahedron, respectively. The cubic framework is generated by sharing the vertices of the octahedra. The framework is exceptionally stable in open air as well as in various solutions including aqueous medium. Most interestingly, the framework constituting Cd(II) ions undergo complete and reversible exchange with Pb(II) in aqueous solution at room temperature without altering structural integrity and losing single crystallinity. We have also studied the complete exchange of framework Cd(II) ions with lanthanide ions (Dy(III) and Nd(III)) with the retention of the framework topology. The reversible exchange of framework constituting metal ions while maintaining the framework integrity and single crystallinity was confirmed by a combination of various methods including ICP-AES, in situ PXRD, TGA, IR, optical microscopy, elemental analysis, N(2) sorption and in situ single crystal X-ray structural analysis.