Search

In this study, a trisodium citrate (TSC)-assisted hydrothermal method is utilized to prepare three-dimensional hydroxyapatite (3D HA). Understanding the role of TSC in the preparation of 3D HA crystals may provide valuable methods to design advanced biomaterials. As one of the indexes of solution supersaturation, the initial pH (ipH) value can not only directly affect the nucleation rate, but also affect the growth of HA crystals. In this work, the effect of the ipH on the microstructure, particle size distribution, and specific surface area of the 3D HA is explored. Results showed that the morphology of 3D HA transformed from a bundle to a dumbbell ball and then a dumbbell with an increase in the ipH. A corresponding mechanism of such a structural evolution was proposed, providing inspiration for the fabrication of innovative 3D HA structures with enhanced biological functionality and performance. [ABSTRACT FROM AUTHOR]

Combining zinc nitrate with 3and/or 4aminocinnamic acid (3-ACA and 4-ACA, respectively) leads to the formation of the 0D complex [Zn(4-AC)2(H2O)2], the 1D coordination polymer [Zn(3-AC)(4-AC)], and the 2D and 3D MOFs [Zn(3AC)2]'2H2O and [Zn(4-AC)2]*H2O, respectively. These compounds result from the deprotonation of the acid molecules, with the resulting 3and 4aminocinnamate anions serving as bidentate terminal or bridging ligands. All solids were fully characterized via single crystal and powder X-ray diffraction and thermal techniques. Given the mild antimicrobial properties of cinnamic acid derivatives and the antibacterial nature of the metal cation, these compounds were assessed and demonstrated very good planktonic cell killing as well as inhibition of biofilm growth against Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus. [ABSTRACT FROM AUTHOR]

Precursor 1 ([Cu.sup.II][([L.sup.SAL]).sub.2]) is used for developing a series of amphiphilic and redox-responsive complexes as candidates for developing responsive films. Core flexibility has improved Langmuir film formation with a higher formal collapse and has showed good cyclability of the ligand-based processes.

The amphiphilic behavior and the molecular structure of cobalt(II)-containing soft-materials with asymmetric tridentate ligands are studied. The complexes are found to exhibit similar amphiphilic, where as different collapse mechanisms.

Three six-coordinate cobalt(III) complexes containing electron-rich phenolato pentadentate [N2O5] ligands were synthesized and characterized, namely, [CoIII(L1)(MeOH)] ( 1), [CoIII(L2)(MeOH)] ( 2) and [CoIII(L3)(MeOH)] ( 3), where L1, L2 and L3 are the triply deprotonated, triply negative form of( E)-6,6′-[({2-[(3,5-di- tert-butyl-2-hydroxybenzylidene)amino]phenyl}azanediyl)bis(methylene)]bis(2,4-di- tert-butylphenol), ( E)-6,6′-[({3-[(3,5-di- tert-butyl-2-hydroxybenzylidene)amino]naphthalen-2-yl}azanediyl)bis(methylene)]bis(2,4-di- tert-butylphenol) and ( E)-6,6′-[({2-[(2-hydroxy-3-methoxybenzylidene)amino]phenyl}azanediyl)bis(methylene)]bis(2,4-di- tert-butylphenol), respectively. Crystal structures were obtained for 1- 3 and reveal a hexacoordinate cobalt(III) ion bound to the [N2O3] donors of each ligand and a methanol molecule occupying the sixth position. The complexes exhibited comparable electronic behavior dominated by phenolate→cobalt charge transfer processes and four redox-accessible states involving three distinct phenolato/phenoxyl radical couples and a fourth process associated with the CoII/CoIII couple. The redox processes were cycled 30 times without major decomposition at the surface of the electrode for 1 and 2, indicating that the oxidized species should be substitutionally inert and do not degrade significantly upon cycling. Electronic-structure DFT calculations on models 1′ and 2′ favor the generation of localized phenoxyl radicals and suggest distinctive oxidation sequences associated to the nature of the ligands. [ABSTRACT FROM AUTHOR]

The lowest energy metal-to-ligand charge transfer (MLCT) absorption bands found in ambient solutions of a series of [Ru(tpy)(bpy)X]m+ complexes (tpy = 2,2′:3′,2″-terpyridine; bpy = 2,2′-bipyridine; and X = a monodentate ancillary ligand) feature one or two partly resolved weak absorptions (bands I and/or II) on the low energy side of their absorption envelopes. Similar features are found for the related cyanide-bridged bi- and trimetallic complexes. However, the weak absorption band I of [(bpy)2Ru{CNRu(tpy)(bpy)}2]4+ is missing in its [(bpy)2Ru{NCRu(tpy)(bpy)}2]4+ linkage isomer demonstrating that this feature arises from a RuII/tpy MLCT absorption. The energies of the MLCT band I components of the [Ru(tpy)(bpy)X]m+ complexes are proportional to the differences between the potentials for the first oxidation and the first reduction waves of the complexes. Time-dependent density functional theory (TD-DFT) computational modeling indicates that these band I components correspond to the highest occupied molecular orbital (HOMO) to lowest unoccupied molecular orbital (LUMO) transition, with the HOMO being largely ruthenium-centered and the LUMO largely tpy-centered. The most intense contribution to a lowest energy MLCT absorption envelope (band III) of these complexes corresponds to the convolution of several orbitally different components, and its absorption maximum has an energy that is about 5000 cm-1 higher than that of band I. The multimetallic complexes that contain RuII centers linked by cyanide have mixed valence excited states in which more than 10% of electronic density is delocalized between the nearest neighbor ruthenium centers, and the corresponding stabilization energy contributions in the excited states are indistinguishable from those of the corresponding ground states. Single crystal X-ray structures and computational modeling indicate that the Ru-(C≡N)-Ru linkage is quite flexible and that there is not an appreciable variation in electronic structure or energy among the conformational isomers. [ABSTRACT FROM AUTHOR]

A correction to the article "Characterization of Low Energy Charge Transfer Transitions in (terpyridine)(bipyridine)Ruthenium(II) Complexes and Their Cyanide-Bridged Bi- and Tri-Metallic Analogues," by Chia-Nung Tsai and colleagues is presented.

Herein, we describe the synthesis and characterization of a novel series of single-tail amphiphiles LPyCn (Py=pyridine, Cn=C18, C16, C14, C10) and their copper(II)-containing complexes, which are of relevance for patterned films. The N-(pyridine-2-ylmethyl)alkyl-1-amine ligands and their complexes [CuIICl2(LPyC18)] (1), [CuIICl2(LPyC16)] (2), [CuIICl2(LPyC14)] (3), [CuIIBr2(LPyC18)] (4), [CuIIBr2(LPyC16)] (5), and [CuIIBr2(LPyC10)] (6) were synthesized, isolated, and characterized by means of mass spectrometry, IR and NMR spectroscopies, and elemental analysis. Complexes 1, 2, 3, and 6 had their molecular structure solved by X-ray diffraction methods, which showed that the local geometry around the metal center is distorted square planar. With the aim of using these species as precursors for redox-responsive films, an assessment of their electrochemical properties involved cyclic voltammetry in different solvents, with different supporting electrolytes and scan rates. Density functional theory calculations of relevant species in bulk and at interfaces were used to evaluate their electronic structure and dipole moments. The morphology and order of the resulting films at the air/water interface were studied by isothermal compression and Brewster angle microscopy. Biphasic patterned Langmuir films were observed for all complexes except 3 and 6, and dependence on the chain length and the nature of the halogen coligand determine the characteristics of the isotherms and their intricate topology. Complexes 3 and 6, which have shorter chain lengths, failed to exhibit organization. These results exemplify the first comprehensive study of the behavior of single-tail metallosurfactants, which are likely to lead to high-end technological applications based on their patterned films.