Shin-ichi Nishikiori

Formation of 1 D and 3 D Coordination Polymers in the Solid State Induced by Mechanochemical and Annealing Treatments: Bis(3‐cyano‐pentane‐2,4‐dionato) Metal Complexes

Bis(3-cyano-pentane-2,4-dionato) (CNacac) metal complex, [M(CNacac)(2)], which acts as both a metal-ion-like and a ligand-like building unit, forms supramolecular structures by self-assembly. Co-grinding of the metal acetates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with CNacacH formed a CNacac complex in all cases: mononuclear complex was formed in the cases of Mn(II), Cu(II) and Zn(II), whereas polymeric ones were formed in the cases of Fe(II), Co(II) and Ni(II). Subsequent annealing converted the mononuclear complexes of Mn(II), Cu(II) and Zn(II) to their corresponding polymers as a result of dehydration of the mononuclear complexes. The resultant Mn(II), Fe(II), Co(II), Ni(II) and Zn(II) polymeric complexes had a common 3 D structure with high thermal stability. In the case of Cu(II), a 1 D polymer was obtained. The Mn(II), Cu(II) and Zn(II) polymeric complexes returned to their original mononuclear complexes on exposure to water vapour but they reverted to the polymeric complexes by re-annealing. Co-grinding of metal chlorides with CNacacH and annealing of the mononuclear CNacac complexes prepared from solution reactions were also examined for comparison. [Mn(CNacac)(2)(H(2)O)(2)], [M(CNacac)(2)(H(2)O)] (M=Cu(II) and Zn(II)) and [M(CNacac)(2)](infinity) (M=Mn(II), Fe(II) and Zn(II)) are new compounds, which clearly indicated the power of the combined mechanochemical/annealing method for the synthesis of varied metal coordination complexes.

Design and Structural Extension of a Supramolecular Inclusion‐Compound Host Made by the Formation of Dimers of Isonicotinic Acid and Thiocyanato Coordinating Bridges

A new host design for an inclusion compound with a preference for large planar aromatic guest molecules has been proposed. Our host design includes a rectangular cavity made using a long and a short building block based on the concept of supramolecular chemistry. The long building block facilitates the inclusion of large guests, and the short building block prevents the formation of an interpenetrated structure, which is often observed in frameworks with large void spaces. The long building block is made when dimers of 4-pyridinecarboxylic acid (isoH) form through hydrogen bonding between the two carboxylic acid moieties. This isoH dimer can link two transition metal centers using the N atoms at both ends to act as a long building block. For the short building block, the thiocyanato ion was used. This makes a bent bridge between two metal centers to form a 1D double-chain [M(SCN)2]infinity complex. From the self-assembly of isoH, SCN- and Ni2+, a 2D network of [Ni(SCN)2(isoH)2]infinity, in which the 1D [Ni(SCN)2]infinity complexes are linked by the isoH dimers, is built up. The rectangular cavity is formed as a mesh within the 2D network. The crystal of our inclusion compound has a layered structure of 2D networks, and a 1D channel-like cavity penetrating the layered 2D networks is formed where guests may be included. Moreover, our host design has the advantage of easy extension of the host structure. Replacement of isoH with another component and use of three components is possible for making the long building block. In the latter case, a linear spacer having two carboxy groups is inserted into the isoH dimer to form a long building block with a trimer structure. Based on our host design, a series of new inclusion compounds were synthesized. The crystal structures of three compounds were determined by single crystal X-ray diffraction. These were a biphenyl inclusion compound [Ni(SCN)2(isoH)2].1/2C12H10 (the basic case), a 9,10-dichloroanthracene inclusion compound [Ni(SCN)2(acrylH)2].1/2C14H8Cl2, where isoH is replaced with 3-(4-pyridinyl)-2-propenoic acid (acrylH), and a perylene inclusion compound [Ni(SCN)2(isoH)2(fumaricH2)].1/2C20H12, whose long building block is a trimer inserted with fumaric acid (fumaricH2) as a linear spacer.

Crystal structures of ethylenediaminecadmium(II) tetracyanocadmate(II)-benzene(1/2) and ethylenediaminecadmium(II) tetracyanocadmate(II)

The crystal structure of ethylenediaminecadmium(II) tetracyanocadmate(II)-benzene(1/2),I, has been redetermined based on 1632 reflections collected anew for the crystal coated with epoxy resin, with a final conventionalR=0.038;I crystallizes in space groupP4222, witha=b=8.265(1) andc=15.512(3) Å, andZ=2. Ethylenediaminecadmium(II) tetracyanocadmate(II),II, is concluded to be identical with the residual metal complex host ofI, remaining after the liberation of the guest benzene molecules;II crystallizes from an aqueous solution containing bis- or tris-ethylenediaminecadmium(II) tetracyanocadmate(II) in space groupI41/acd, witha=b=14.366(1) andc=23.771(4) Å, andZ=16; refinement led to a conventionalR=0.043 for 1181 reflections. The bridging ethylenediamine ligand inI turns to a chelating one inII; dissociation and recombination should occur in the coordination sphere of the six-coordinate cadmium atom, whenII is derived fromI by the liberation of the guest molecules.

Three Polymorphic CdII Coordination Polymers Obtained from the Solution and Mechanochemical Reactions of 3‐Cyanopentane‐2,4‐dione with CdII Acetate

We previously reported that monomeric and polymeric metal complexes are obtained from solution and mechanochemical reactions of 3-cyano-pentane-2,4-dione (CNacacH) with 3d metal acetates (M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II)). A common feature found in all complexes was that their structural base is trans-[M(CNacac)(2)]. Here, we report that the reactions of CNacacH with Cd(II) acetate in the solution and solid states afford different coordination polymers composed of trans-[Cd(CNacac)(2)] and cis-[Cd(CNacac)(2)] units, respectively. From a methanol solution containing CNacacH (L) and Cd(OAc)(2)⋅2 H(2)O (M), a coordination polymer (Cd-1) in which trans-[Cd(CNacac)(2)] units are three-dimensionally linked was obtained. In contrast, two different coordination polymers, Cd-2 and Cd-3, were obtained from mechanochemical reactions of CNacacH with Cd(OAc)(2)⋅2 H(2)O at M/L ratios of 1:1 and 1:2, respectively. In Cd-2, cis-[Cd(CNacac)(2)] units are two-dimensionally linked, whereas the units are linked three-dimensionally in Cd-3. Furthermore, Cd-1 and Cd-2 converted to Cd-3 by applying an annealing treatment and grinding with a small amount of liquid, respectively, in spite of the polymeric structures. These phenomena, 1) different structures are formed from solution and mechanochemical reactions, 2) two polymorphs are formed depending on the M/L ratio, and 3) structural transformation of resulting polymeric structures, indicate the usability of mechanochemical method in the syntheses of coordination polymers as well as the peculiar structural flexibility of cadmium-CNacac polymers.

The crystal structures of α, ω-diaminoalkanecadmium(II) tetracyanonickelate(II)-Aromatic molecule inclusion compounds. V. Toluidine clathrates of the hosts built of the diamines, 1,4-diaminobutane, 1.5-diaminonentane, and 1,8-diaminooctane

The crystal structures have been analyzed for the threeo-toluidine clathrates,catena-[catena-μ-(1,4-diaminobutane)cadmium(II) tetra-μ-cyanonickelate(II)]-o-toluidine(2/3),4-o,catena-[catena-μ-(1,5-diaminopentane)cadmium(II) tetra-μ-cyanonickelate(II)]-o-toluidine(3/4),5-o, andcatena-[catena-μ-(1,8-diaminooctane)cadium(II) tetra-μ-cyanonickelate(II)]-o-toluidine(1/1),8-o, for am-toluidine onecatena-[catena-μ-(1,5-diaminopentane)cadmium(II) tetra-μ-cyano-nickelate(II)]-m-toluidine(1/1),5-m, and for ap-toluidine onecatena-[catena-μ-(1,8-diaminooctane)cadium(II) tetra-μ-cyanonickelate(II)]-p-toluidine(1/1),8-p. 4-o crystallizes in the triclinic space groupPī,a/Å = 9.806(3),b/Å = 14.388(3),c/Å = 7.725(2), α/° = 89.71(2), β/° = 89.96(2), γ/° = 98.12(2),V/Å3 = 1078.8(5),Z = 2, 3750 reflections,R = 0.056;5-o: tetragonalP4lmmm, (a = b)/Å = 7.485(7),c/Å = 10.06(3),V/Å3 = 563(2),Z = 1, 573 reflections,R = 0.19;8-o: monoclinicP2/m,a/Å = 11.513(4),b/Å = 7.626(1),c/Å = 7.101(1), β/° = 109.63(3),V/Å3 = 587.2(2),Z = 1, 1682 reflections,R = 0.058;5-m: orthorhombicPbam,a/Å = 12.254(6),b/Å = 20.62(1),c/Å = 7.804(1),V/Å3 = 1972(1),Z = 4, 2240 reflections,R = 0.059; and8-p: triclinic,Pī,a/Å = 11.52(1),b/Å = 7.632(3),c/Å = 7.039(4), α/° = 88.93(4), β/° = 109.71(5), γ/° = 82.81(9),V/Å3 = 576.9(6),Z = 1, 2598 reflections,R = 0.042. Their structures are substantially similar to the already-known structure ofcatena-[catena-μ-(1,6-diaminohexane)cadmium(II) tetra-μ-cyanonickelate(II)]-o-toluidine(1/1): the guest toluidine molecules are accommodated in the cavities formed betweencatena-[cadmium(II) tetra-μ-cyanonickelate(II)] layers bridged by the ambidentate α,ω-diaminoalkane ligands at the cadmium(II) atoms. The carbon chain length of the α,ω-diaminoalkane influences the number of cavities per formula unit and the deformation of the metal complex layers.

Synthesis and crystal structure of bis(ethylenediamine)-diisothiocyanatonickel(II)–benzene: a new ‘Werner-type’ clathrate compound

The purple complex clathrate [Ni(en)2(NCS)2]·C6H6 is the first example of an inclusion compound based on a bis(bidentate amine) octahedral complex host.

Bis(3-cyano-pentane-2,4-dionato) Co(II) as a linear building block for coordination polymers: combinations with two polypyridines

Two types of bis(β-diketonato) Co(II) complexes, [Co(CNacac)2] (CNacac = 3-cyano-pentane-2,4-dionato), and [Co(dbm)2] (dbm = dibenzoylmethanato or 1,3-diphenyl-propane-1,3-dionato) were examined as linear building blocks for the construction of coordination polymers in combination with two oligopyridines, 1,4-bis(4,2’:6’,4”-terpyridin-4’-yl)benzene (L1) and 1,3-bis(3,2’:6’,3”-terpyridin-4’-yl)benzene) (L2). From combinations of [Co(CNacac)2] with L1 and L2, 2-D coordination polymers, [Co(CNacac)2]2(L1)·(CHCl3)·(CH3OH) (CoCN-1) and [Co(CNacac)2](L2)1/2·(tetrachloroethane)3/2 (CoCN-2), are obtained. Both CoCN-1 and CoCN-2 have 2D (4,4) net structures, in which L1 and L2 are tetradentate. In contrast, combination of [Co(dbm)2] with L2 affords a 1-D coordination polymer, [Co(dbm)2](L2)·4(CH3OH) (Codbm-1), in which L2 is bidentate. L2 as a tetradentate ligand was inhibited by bulky phenyl rings in [Co(dbm)2]. These results indicate that [Co(CNacac)2] with a relatively simplified structure is useful as a linear building block in combinations with bulky oligopyridines.

Adsorption and separation of poly-aromatic hydrocarbons by a hydrogen-bonded coordination polymer.

A residual-host prepared by thermal removal of naphthalene (NA) from the inclusion compound [Ni(SCN)(2)(isonicotinic acid)(2)]·(NA)(0.5) was found to function as an adsorbent for aromatic molecules and exhibit method-dependent selectivity.

Orientation of guest benzene molecules in Hofmann-type and related clathrates by molecular mechanics calculation

Molecular mechanics calculations were carried out to interpret the observed orientational angle of the benzene molecule enclathrated in the Hofmann-type M(NH3)2Ni(CN)4·2 C6H6 (M = Mn, Ni, Cu, and Cd), Hofmann-en-type Cd(en)Ni(CN)4·2 C6H6 (en = NH2CH2CH2NH2), and Hofmannmea-type(2) Cd(mea)Ni(CN)4·2 C6H6 (mea = NH2CH2CH2OH) clathrates using the van der Waals potential functions in Molecular Mechanics Version 2. The angle is most influenced by the guest-to-guest contact in the interlayer space between the two-dimensionalcatena-[metal(II) tetra-μ-cyanonickelate(II)] networks for the Hofmann-type series. The discrepancy between the calculated and the observed angles in each crystal structure was at largest 3.5°; the structures of Cd(NH3)2Ni(CN)4·2 C6H6 and Cd(en)Ni(CN)4·2 C6H6 have been revised using new data collected by counter-methods.

X-ray and 2H NMR studies of structure and dynamics in the Hofmann-type and the Hofmann-(en)-type pyrrole clathrates

Abstract Structure and dynamics in the Hofmann and Hoffmann-en type pyrrole clathrates, Cd(NH3)2Ni(CN)4·2C4H4NH and Cd(en)Ni(CN)4·2C4H4NH, have been studied by single crystal X-ray crystallography, solid state 2H NMR, PXRD, TGA and DSC. Both show in-plane reorientation of the pyrrole in an inequivalent six-site potential, with two low energy minima where the N of the pyrrole is oriented up or down with respect to the crystal c axis, followed by out-of-plane 4-fold motion about an axis parallel to the crystal c axis. There is also evidence for an intermediate dynamic state where there is 2-fold rather than 4-fold motion. The NH3 or en groups of the host frameworks rotate about the crystal c direction. The Hofmann-en pyrrole clathrate shows two phase transitions at 196 and 259 K, and the dynamics of the host en and pyrrole guest appear to be intimately linked to the latter structural transition. The results for these pyrrole clathrates have been compared with those for the two equivalent benzene clathrates, obtained previously and augmented with new 2H NMR lineshape data for Cd(en)Ni(CN)4·2C6D6 above 300 K.