Deamination of the amino acid fragment in imine metallacycles: unexpected synthesis of an NH-aldimine organometallic compound

We report that the action of Lewis bases, such as triphenylphosphine, pyridine, or trimethylamine, on imine metallacycles derived from amino acids leads to the formation of the first organometallic compound of an NH aldimine, a highly reactive organic species, and the corresponding alpha-ketoester, in a deamination reaction that mimics the metabolism of alpha-amino acids. The synthesis of different cyclopalladated compounds by a reaction between palladium acetate and the Schiff bases 2,4,6-Me(3)C(6)H(2)CH=NCH(R(1))COOR(2) (R(1) = CH(2)Ph, R(2) = Et and R(1) = Ph, R(2) = Me) is also reported.     

Synthesis and biological evaluation of indoloquinolines and pyridocarbazoles: a new example of unexpected photoreduction accompanying photocyclization

Indoloquinoline alkaloid cryptolepine and pyridocarbazole alkaloid ellipticine are of great interest because in vitro and in vivo studies revealed their good cytotoxic properties. In order to obtain some biologically active analogs of these compounds, we developed a synthesis based on the photocyclization of tertiary N-substituted enaminones derived from 1,3-cyclohexandione and 3 or 6-aminoquinoline. The angular cyclized compounds thus obtained were tested in vitro on K 562 cells and A 2780 doxorubicin sensitive and resistant cells. All compounds were less effective than doxorubicin in sensitive cells but their activity wasn't decreased by MDR resistance.     

Self-assembled nanospheres as a novel delivery system for taxol: a molecular hydrogel with nanosphere morphology

Here we reported on the first example of a Folic acid-based molecular hydrogel with nanosphere morphology as a delivery system for Taxol.     

A new type of photodegradable polymer having a pyrazine moiety in the chain

Photooxidative degradation of poly-2,5-distyrylpyrazine (poly-DSP) has been studied in detail. Both amorphous poly-DSP film and poly-DSP solution were photooxygenated and degraded by irradiation by sunlight in the air. The nitrile group was formed, together with carbonyl groups and hydroxyl group. The photodegradation of a pyrazine derivative to a nitrile derivative is a new reaction. Next, photodegradation behavior of polymers having a cyclobutane moiety in the main chain, poly-1,4-bis[2-(2-pyridyl)-vinyl]benzene (poly-P2VB) and polydiethyl p-phenylenediacrylate (poly-p-PDA Et), was studied. The photodegradability of these polymers decreases in the order: poly-DSP > poly-P2VB ? poly-p-PDA Et. Further, the photodegradation behavior of various vinyl polymers containing a vinylpyrazine or vinylpyridine component and polyamides having pyrazine or pyridine ring in the main chain, was investigated. Of these, polyvinylpyrazine has the largest photodegradability.     

Self-assembled monolayer electrode of a diiron complex with a phenoxo-based dinucleating ligand: observation of molecular oxygen adsorptionldesorption in aqueous media

The phenoxo-based dinucleating ligand, 2,6-bis[bis(6-pivalamido-2-pyridylmethyl)amino-methyl-4-aminophenol (1), and its Fe2(II) complex, [Fe2(II)(1)(PhCOO)2](CF3SO3) (2), were prepared and 2 deposited on the Au surface (2/Au) is much more stable than in solution and exhibits redox behavior in aqueous media as well as reversible adsorption/desorption of oxygen at room temperature.     

Extending molecular dynamics time scales with milestoning: example of complex kinetics in a solvated peptide

A recently introduced computational algorithm to extend time scales of atomically detailed simulations is illustrated. The algorithm, milestoning, is based on partitioning the dynamics to a sequence of trajectories between "milestones" and constructing a non-Markovian model for the motion along a reaction coordinate. The kinetics of a conformational transition in a blocked alanine is computed and shown to be accurate, more efficient than straightforward molecular dynamics by a factor of about 9, and nonexponential. A general scaling argument predicts a linear speedup with the number of milestones for diffusive processes and an exponential speedup for transitions over barriers. The algorithm is also trivial to parallelize. As a side result, milestoning also produces the free energy profile along the reaction coordinate and is able to describe nonequilibrium motions along one (or a few) degrees of freedom.     

Self-assembled molecular squares containing metal-based donor: synthesis and application in the sensing of nitro-aromatics

Self-assemblies between a linear Pt-based donor and ferrocene- chelated metallic acceptors produced novel heterometallic squares 4 and 5, which show fluorescence quenching upon the addition of nitro-aromatics.     

First example of the activation of polymethylhydrosiloxane with molecular iodine: a facile synthesis of 3,6-dihydropyran derivatives

Glycals react rapidly with polymethylhydrosiloxane (PMHS) in the presence of a catalytic amount of molecular iodine under mild conditions to afford the corresponding 3,6-dihydropyran derivatives in excellent yields. Et₃SiH/I₂ was also found to be effective for this conversion.     

Dynamic molecular recognition in the generation of a new crystal-engineering motif: a unique case study of a dicarboxylic acid with a ditopic receptor favouring a polymeric over a dimeric hydrogen-bonded supramolecular complex

A new crystal-engineering motif has been developed where a ditopic receptor 1 shows a novel syn-syn hydrogen-bonded polymeric supramolecular complex (Fig. 4b) (instead of a 1:1 dimeric syn-syn or polymeric syn-anti complex) giving rise to a hydrogen-bonded stair-like polymeric ribbon structure between the binding groups of the receptor pyridine amide and the carboxyl groups of the guest substrate.     

Binaphthalene with substituted tetrathiafulvalene and trichloroquinone: a new example of metal ion-promoted electron transfer

A new binaphthalene (R)-1 with two substituted TTF and trichloroquinone units is reported. Both absorption and ESR spectral studies show that electron transfer occurs between TTF and trichloroquinone units of (R)-1 in the presence of metal ions (Pb²⁺, Sc³⁺, Zn²⁺, and Ca²⁺). We also propose a possible mechanism for this electron transfer process. But, the CD spectral change of (R)-1 in the presence of metal ions is rather small.     

Lanthanides in molecular magnetism: old tools in a new field

In this tutorial review we discuss some basic aspects concerning the magnetic properties of rare-earth ions, which are currently the subject of a renovated interest in the field of molecular magnetism, after the discovery that slow relaxation of the magnetization at liquid nitrogen temperature can occur in mononuclear complexes of these ions. Focusing on Dy(III) derivatives a tutorial discussion is given of the relation of the crystal field parameters, which determine the anisotropy of these systems and consequently their interesting magnetic properties, with the geometry of the coordination sphere around the lanthanide centre and with the pattern of f orbitals. The problem of systems of low point symmetry is also addressed by showing how detailed single crystal investigation, coupled to more sophisticated calculation procedures, is an absolute necessity to obtain meaningful structure-property relationships in these systems.     

Synthesis and mesomorphic properties of a new chiral series with a heterocycle in the molecular core

We report a number of different homologous series with a heterocycle incorporated in the molecular core near the chiral chain. Two of these series differ in the type of chiral chain, -CH*(CH 3 )C 6 H 13 or -CH*(CH 3 )-CO 2 -C 4 H 9 . Their properties are compared and found to show completely different polymorphism. The first series exhibits only SmC* and SmA phases whereas the second possesses TGB, N* and BP phases. The mesomorphic properties were studied by optical microscopy, DSC and electro-optical measurements. The effect of substitution of the phenyl ring near the chiral chain by a heterocycle is discussed.     

Synthesis and mesomorphic properties of a new chiral series with a heterocycle in the molecular core

We report a number of different homologous series with a heterocycle incorporated in the molecular core near the chiral chain. Two of these series differ in the type of chiral chain, -CH*(CH₃)C₆H₁₃ or -CH*(CH₃)-CO₂-C₄H₉. Their properties are compared and found to show completely different polymorphism. The first series exhibits only SmC* and SmA phases whereas the second possesses TGB, N* and BP phases. The mesomorphic properties were studied by optical microscopy, DSC and electro-optical measurements. The effect of substitution of the phenyl ring near the chiral chain by a heterocycle is discussed.     

Light-driven molecular hinge: a new molecular machine showing a light-intensity-dependent photoresponse that utilizes the trans-cis isomerization of azobenzene

[reaction: see text] A new class of molecular machine exhibits a hingelike motion upon photoirradiation. The motion (close and open) can be operated by alternate irradiation with UV and visible light. The trans/trans and cis/cis isomers are thermally stable at 40 degrees C, and the photochemical closure reaction (from trans/trans to cis/cis isomer) is dependent on the intensity of the light used because of the short-lived intermediate (trans/cis isomer).     

Operation of micro and molecular machines: a new concept with its origins in interface science

A landmark accomplishment of nanotechnology would be successful fabrication of ultrasmall machines that can work like tweezers, motors, or even computing devices. Now we must consider how operation of micro- and molecular machines might be implemented for a wide range of applications. If these machines function only under limited conditions and/or require specialized apparatus then they are useless for practical applications. Therefore, it is important to carefully consider the access of functionality of the molecular or nanoscale systems by conventional stimuli at the macroscopic level. In this perspective, we will outline the position of micro- and molecular machines in current science and technology. Most of these machines are operated by light irradiation, application of electrical or magnetic fields, chemical reactions, and thermal fluctuations, which cannot always be applied in remote machine operation. We also propose strategies for molecular machine operation using the most conventional of stimuli, that of macroscopic mechanical force, achieved through mechanical operation of molecular machines located at an air-water interface. The crucial roles of the characteristics of an interfacial environment, i.e. connection between macroscopic dimension and nanoscopic function, and contact of media with different dielectric natures, are also described.     

Self-assembled monolayers of optically active Co(III) complexes: a new promoter electrode recognizing the electron transfer site in cytochrome c

A new-class of promoter electrode bearing a molecular recognition ability has been constructed; the chirality and/or orientation of promoter on the Au electrode surface have affected the electron transfer rate of cytochrome c.