A metal-organic bilayer open framework with a dynamic component: single-crystal-to-single-crystal transformations

A metal-organic bilayered open framework, [Ni2(C26H52N10)]3[BTC]4.6C5H5N.36H2O (BOF-1, 1), has been prepared by the self-assembly of a new bismacrocyclic nickel(II) complex [Ni2(C26H52N10)(Cl)4].H2O (A) and sodium 1,3,5-benzenetricarboxylate (Na3BTC) in the mixture of water/DMSO/pyridine. The X-ray crystal structure of 1 shows that 2D layers with the cavities of brick-wall motifs (22.6 x 14.3 A2) are formed by the coordination of the nickel(II) complex with BTC3- ions and that the two 2D layers are linked with the p-xylyl bridging groups of the bismacrocycles as pillars to generate 3D channels in the bilayered framework. The voids of the channels occupy 61% of the total volume, which are filled with pyridine and water guest molecules. When 1 was dried at 75 degrees C for 1.5 h, [Ni2(C26H52N10)]3[BTC]4.4H2O (2) resulted by maintaining the single-crystallinity, which exhibited a dramatic decrease in the interlayer spacing as well as changes in the cell parameters. Solid 2 differentiates various alcohols such as MeOH, EtOH, isopropyl alcohol, and benzyl alcohol in toluene. When 1 was immersed in insoluble solvents such as pyridine and benzene, some guest molecules were exchanged with the aromatic molecules to give [Ni2(C26H52N10)]3[BTC]4.20pyridine.6H2O (3) and [Ni2(C26H52N10)]3[BTC]4.14benzene.19H2O (4), respectively. The guest-exchange processes also involve single-crystal-to-single-crystal transformation.     

Vitamin D side chain triazole analogs via cycloaddition `click' chemistry

Cycloaddition of a vitamin D side chain terminal acetylene with phenyl azide and separately with a vitamin D side chain terminal azide produced the corresponding 1,2,3-triazole monomeric and dimeric analogs of 1α-hydroxyvitamin D₃ in good yields.     

Investigation of the scanning tunneling microscopy image, the stacking pattern, and the bias-voltage-dependent structural instability of 1,10'-phenanthroline molecules adsorbed on Au(111) in terms of electronic structure calculations

A self-assembled monolayer of 1,10'-phenanthroline (phen) molecules on Au(111) was found to undergo a structural phase transition when the bias voltage is switched in scanning tunneling microscopy (STM) experiments (Phys. Rev. Lett. 1995, 75, 2376; Surf. Sci. 1997, 389, 19). The nature of two bright spots representing each phen molecule in the high-resolution STM images of phen molecules on Au(111) was identified by calculating the partial density plots for a monolayer of phen molecules adsorbed on Au(111) with tight-binding electronic structure calculations. The stacking pattern of chains of phen molecules on Au(111) was explained by studying the intermolecular interactions between phen molecules on the basis of first-principles electronic structure calculations for a phen dimer, (phen)(2). The structural instability of phen molecule arrangement caused by the bias-voltage switch was probed by estimating the adsorbate-surface interaction energy with the point-charge approximation for Au(111).     

A hybrid consisting of coordination polymer and noncovalent organic networks: a highly ordered 2-D phenol network assembled by edge-to-face pi-pi interactions

A 2-D metal-organic open framework having 1-D channels, [Cu(C(10)H(26)N(6))](3)[C(6)H(3)(COO)(3)](2).18H(2)O (1), was constructed by the self-assembly of the Cu(II) complex of hexaazamacrocycle A (A = C(10)H(26)N(6)) with sodium 1,3,5-benzenetricarboxylate (BTC(3)(-)) in DMSO-H(2)O solution. 1 crystallizes in the trigonal space group P with a = b = 17.705(1) A, c = 6.940(1) A, alpha = beta = 90 degrees, gamma = 120 degrees, V = 1884.0(3) A(3), Z = 1, and rho(calcd) = 1.428 g cm(-3). The X-ray crystal structure of 1 indicates that each Cu(II) macrocyclic unit binds two BTC(3-) ions in a trans position and each BTC(3-) ion coordinates three Cu(II) macrocyclic complexes to form 2-D coordination polymer layers with honeycomb cavities (effective size 8.1 A), and the layers are packed to generate 1-D channels perpendicularly to the 2-D layers. Solid 1 binds guest molecules such as MeOH, EtOH, and PhOH with different binding constant and capacity. By the treatment of 1 with aqueous solution of phenol, a hybrid solid [Cu(C(10)H(26)N(6))](3)[C(6)H(3)(COO)(3)](2).9PhOH.6H(2)O (2) was assembled. 2 crystallizes in the trigonal R3 space group with a = b = 20.461(1) A, c = 24.159(1) A, alpha = beta = 90 degrees, gamma = 120 degrees, V = 8759.2(7) A(3), Z = 3, and rho(calcd) = 1.280 g cm(-3). In 2, highly ordered 2-D noncovalent phenol layers are formed by the edge-to-face pi-pi interactions between the phenol molecules and are alternately packed with the coordination polymer layers in the crystal lattice.     

Reaction monitoring of succinylation of collagen with matrix-assisted laser desorption/ionization mass spectrometry

Succinylated collagen was synthesized by the reaction of collagen with succinic anhydride under basic conditions for one hour. Using the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) technique, the reaction products were directly identified without multi-step separation processes. MALDI-MS monitored the reaction more accurately than the conventional method of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). From the change in molecular mass during the reaction, it is observed that about 28 succinyl groups are attached to the collagen strand.     

Nickel(II) macrocyclic complexes with long alkyl pendant chain: synthesis,x-ray structure,and anion exchange property in the solid state

A nickel(II) pentaaza macrocyclic complex containing a 1-hexadecyl pendant chain, [Ni(C(25)H(55)N(5))](ClO(4))(2).H(2)O (1), was synthesized by a one-pot metal-template condensation reaction. Crystal data for 1: triclinic, Ponemacr;, a = 8.333(4) A, b = 8.356(3) A, c = 28.374(9) A, alpha = 81.865(19) degrees, beta = 86.242(18) degrees, gamma = 63.871(17) degrees, Z = 2. Solid 1 forms hydrophobic layers that are constructed by the long alkyl chains of the macrocycles. Solid 1 exchanges ClO(4)(-) with NCS(-), PF(6)(-), C(2)O(4)(2-), NO(3)(-), and CF(3)SO(3)(-) that are dissolved in water. From the reaction of [Ni(C(25)H(55)N(5))Cl(2)] with Et(3)NH(TCNQ)(2) in EtOH/DMF/acetone solution, [Ni(C(25)H(55)N(5))(TCNQ)(2)](TCNQ).(CH(3)COCH(3)) (2) (TCNQ = 7,7,8,8-tetracyano-p-quinodimethane) was prepared. Crystal data for 2: triclinic, Ponemacr;, a = 8.459(0) A, b = 13.945 (1) A, c = 26.833(2) A, alpha = 88.744(2) degrees, beta = 84.536(2) degrees, gamma = 80.089(4) degrees, Z = 2. In 2, TCNQ anions coordinate nickel(II) at the axial sites, which form pi-stacked TCNQ(-) dimers to give rise to 1-D chains. The neutral TCNQ molecules are included between the dimerized TCNQ(-) species, which construct a pi-stacked group of six TCNQ units as blocked by the long alkyl chains. Compound 2 is an electric insulator. It shows a weak signal in the EPR spectrum. The magnetic susceptibility data of 2 measured at 5-300 K exhibit a simple paramagnetism at low temperatures (<100 K) but an increase in the magnetic moment at higher temperatures due to the contribution of a thermally accessible triplet state for the antiferromagnetically coupled [TCNQ](2)(2-).     

Synchronization of chaos in simultaneous time-frequency domain

Synchronization of chaos presents many challenges for controller design. The novel notion of exerting concurrent control in the joint time-frequency domain is applied to formulate a chaos synchronization scheme that requires no linearization or heuristic trial-and-errors for nonlinear controller design. The concept is conceived through recognizing the basic attributes inherent of all chaotic systems, including the simultaneous deterioration of dynamics in both the time and frequency domains when bifurcates, nonstationarity, and sensitivity to initial conditions. Having its philosophical bases established in simultaneous time-frequency control, on-line system identification, and adaptive control, the chaos synchronization scheme incorporates multiresolution analysis, adaptive filters, and filtered-x Least Mean Square algorithm as its physical features. Without A priori knowledge of the driven system parameters, synchronization is invariably achieved regardless of the initial and forcing conditions the response system is subjected to. In addition, driving and driven trajectories are seen robustly synchronized with negligible errors in spite of the infliction of high frequency noise.