Ultrafast photoinduced electron transfer in the micelle and the gel phase of a PEO-PPO-PEO triblock copolymer

Ultrafast photoinduced electron transfer (PET) from N,N-dimethylaniline (DMA) to coumarin dyes is studied in the micelle and the gel phase of a triblock copolymer, (PEO)(20)-(PPO)(70)-(PEO)(20) (Pluronic P123) by picosecond and femtosecond emission spectroscopies. The rate of PET in a P123 micelle and gel is found to be nonexponential and faster than the slow components of solvation dynamics. In a P123 micelle and gel, PET occurs on multiple time scales ranging from a subpicosecond time scale to a few nanoseconds. In the gel phase, the highest rate constant (9.3 x 10(9) M(-1) s(-1)) of ET for C152 is about two times higher than that (3.8 x 10(9) M(-1) s(-1)) observed in micelle phase. The ultrafast components of electron transfer (ET) exhibits a bell shaped dependence with the free energy change which is similar to the Marcus inversion. Possible reasons for slower PET in P123 micelle compared to other micelles and relative to P123 gel are discussed.     

Excitation wavelength dependence of solvation dynamics in a supramolecular assembly: PEO-PPO-PEO triblock copolymer and SDS

The triblock copolymer (PEO)20-(PPO)70-(PEO)20 (P123) forms a supramolecular aggregate with sodium dodecyl sulfate (SDS). The solvation dynamics and anisotropy decay of coumarin 480 (C480) in different regions of a P123-SDS aggregate are studied through variation of the excitation wavelength (lambdaex) using femtosecond upconversion. In a P123 micelle, because of the drastic differences in polarity between the hydrophilic corona region (PEO block) and the hydrophobic PPO core, C480 exhibits a pronounced red edge excitation shift (REES) of emission maximum by 24 nm. In the P123-SDS aggregate, SDS penetrates the core of the P123 micelle. This increases the polarity of the core and reduces the difference in the polarity between the core and the corona region. In a P123-SDS aggregate, the REES is much smaller (5 nm) which suggests a reduced difference between the core and the corona. Solvation dynamics in a P123 micelle displays a bulklike ultrafast component (<0.3 and 1 ps) in the PEO corona region, a 200 ps component arising from dynamics of polymer segments, and a very long component (5000 or 3000 ps) due to the highly restricted PPO core. In a P123-SDS aggregate, at lambdaex = 375 and 405 nm, the solvation dynamics is found to be faster than that in P123 micelle. In this case, the component (3000 ps) arising from the core region is faster than that (5000 ps) in P123 micelle. In both P123 micelle and P123-SDS aggregate, the relative contribution of the core region decreases and that of the corona region increases with an increase in lambdaex. At lambdaex = 435 nm, which probes the hydrophilic corona, the solvation dynamics for both P123 micelle and P123-SDS aggregate are almost similar.     

Local environments of coumarin dyes within mesostructured silica-surfactant nanocomposites

The local environments surrounding dye molecules were studied with use of coumarin dyes in a mesostructured silica-surfactant nanocomposite, which was formed in a porous alumina membrane by a surfactant-templated method and has an average pore diameter of 3.4 nm. Coumarin dyes, such as coumarin 480 (C480), coumarin 343 (C343), and propylamide coumarin 343 (PAC343), were extracted into the silica-surfactant nanocomposite and time-resolved fluorescence spectra of these dyes were examined. C480 and C343 show slow dynamic Stokes shifts and the decay curve can be fitted by a biexponential function. The decay-time constants obtained from the fitting are almost identical for C480 and C343: 0.87 and 7.5 ns for C480, and 0.86 and 7.6 ns for C343. In contrast to these two coumarin dyes, short decay-time constants (0.50 and 4.8 ns) were obtained for PAC343 in the silica-surfactant nanocomposite. These results indicate that the local environments of C480 and C343 are almost identical but different from that of PAC343. By considering the origin of the dynamic Stokes shift and the mesostructure of the silica-surfactant nanocomposite, the location and microenvironment of coumarin dyes within the silica-surfactant nanocomposite are discussed.     

Diffusion of organic dyes in a niosome immobilized on a glass surface using fluorescence correlation spectroscopy

Giant multilameller niosomes containing cholesterol and triton X-100 are studied using fluorescence correlation spectroscopy (FCS). Dynamic light scattering (DLS) data indicates formation of niosomes of broadly two different sizes (diameter)--~150 nm and ~1300 nm. This is confirmed by field emission scanning electron microscopy (FE-SEM) and confocal microscopy. The diffusion coefficient (D(t)) of three organic dyes in the niosome immobilized on a glass surface is studied using fluorescence correlation spectroscopy. On addition of the room temperature ionic liquids (RTIL) (1-methyl-3-pentylimidazolium bromide, [pmim][Br] and 1-methyl- 3-pentylimidazolium tetra-fluoroborate, [pmim][BF(4)]) the size of the niosome particles increases. The D(t) of all the organic dyes (DCM, C343 and C480) increases on addition of RTILs, indicating faster diffusion. The viscosity calculated from the D(t) of the three dyes exhibits weak probe dependence. Unlike lipid or catanionic vesicle, the D(t) values in a niosome exhibit very narrow distribution. This indicates that the niosomes are fairly homogeneous with small variation of viscosity.     

Solvation dynamics in ionic liquid swollen p123 triblock copolymer micelle: a femtosecond excitation wavelength dependence study

Femtosecond solvation dynamics of coumarin 480 (C480) in a mixed micelle is reported. The mixed micelle consists of a triblock copolymer (PEO)20-(PPO) 70-(PEO)20 (Pluronic P123) and an ionic liquid (IL), 1-pentyl-3-methylimidazolium tetrafluoroborate ([pmim][BF4]). At a low concentration (0.3 M), the sparingly water soluble IL ([pmim][BF4]) penetrates the hydrophobic PPO core of the P123 micelles. Thus emission maximum of C480 in the core (accessed at lambdaex=375 nm) in 0.3 M IL is red-shifted by 8 nm from that in its absence and the red edge excitation shift (REES) is large (19+/-1 nm). At a high concentration (0.9 M), the ionic liquid [pmim][BF4] invades both the core and corona region and the mixed micelle exhibits very small REES (3+/-1 nm). Anisotropy decay and solvation dynamics in different regions of the mixed micelle are studied by variation of excitation wavelength (lambda ex). In P123 micelle, the average rotational time () is 2800 ps in the core (at lambdaex=375 nm) and 1350 ps in the corona region (at lambdaex=435 nm). In 0.3 M [pmim][BF4], tau rot at the core of the mixed micelle decreases to 1950 ps while that in the corona remains unaffected. In 0.9 M IL, both the core and corona (lambda ex=375 and 435 nm) exhibit similar and short approximately 600 ps. In 0.3 M IL, solvation dynamics in the core region (lambdaex=375 nm) of P123 micelle is about 2 times faster than in its absence. In 0.3 M IL, solvation dynamics in the corona region (lambdaex=435 nm) is approximately 100 times faster than that in the core. In 0.9 M IL, the solvation dynamics in the core and in the corona is, respectively, approximately 9 times and 4 times faster than that in 0.3 M IL.     

Ultrafast fluorescence resonance energy transfer in the micelle and the gel phase of a PEO-PPO-PEO triblock copolymer: excitation wavelength dependence

Fluorescence resonance energy transfer (FRET) from coumarin 480 (C480) to rhodamine 6G (R6G) is studied in the micelle and the gel phase of a triblock copolymer, (PEO)20-(PPO)70-(PEO)20 (Pluronic P123 (P123)) by picosecond and femtosecond emission spectroscopy. The time constants of FRET were obtained from the rise time of the acceptor (R6G) emission. In a P123 micelle, FRET occurs in multiple time scales: 2.5, 100, and 1700 ps. In the gel phase, three rise components are observed: 3, 150, and 2600 ps. According to a simple F?rster model, the ultrafast (2.5 and 3 ps) components of FRET correspond to donor-acceptor distance RDA=13 +/- 2 A. The ultrafast FRET occurs between a donor and an acceptor residing at close contact at the corona (PEO) region of a P123 micelle. With increase in the excitation wavelength (lambdaex) from 375 to 435 nm, the relative contribution of the ultrafast component of FRET ( approximately 3 ps) increases from 13% to 100% in P123 micelle and from 1% to 100% in P123 gel. It is suggested that at lambdaex = 435 nm, mainly the highly polar peripheral region is probed where FRET is very fast due to close proximity of the donor and the acceptor. The 100 and 150 ps components correspond to RDA = 25 +/- 2 A and are ascribed to FRET from C480 deep inside the micelle to an acceptor (R6G) in the peripheral region. The very long component of FRET (1700 ps in micelle and 2600 ps component in gel) may arise from diffusion of the donor from outside the micelle to the interior followed by fast FRET.     

Dynamic processes in a silicate liquid from above melting to below the glass transition

We collect and critically analyze extensive literature data, including our own, on three important kinetic processes--viscous flow, crystal nucleation, and growth--in lithium disilicate (Li(2)O·2SiO(2)) over a wide temperature range, from above T(m) to 0.98T(g) where T(g) ≈ 727 K is the calorimetric glass transition temperature and T(m) = 1307 K, which is the melting point. We found that crystal growth mediated by screw dislocations is the most likely growth mechanism in this system. We then calculated the diffusion coefficients controlling crystal growth, D(eff)(U), and completed the analyses by looking at the ionic diffusion coefficients of Li(+1), O(2-), and Si(4+) estimated from experiments and molecular dynamic simulations. These values were then employed to estimate the effective volume diffusion coefficients, D(eff)(V), resulting from their combination within a hypothetical Li(2)Si(2)O(5) "molecule". The similarity of the temperature dependencies of 1/η, where η is shear viscosity, and D(eff)(V) corroborates the validity of the Stokes-Einstein/Eyring equation (SEE) at high temperatures around T(m). Using the equality of D(eff)(V) and D(eff)(η), we estimated the jump distance λ ~ 2.70 ? from the SEE equation and showed that the values of D(eff)(U) have the same temperature dependence but exceed D(eff)(η) by about eightfold. The difference between D(eff)(η) and D(eff)(U) indicates that the former determines the process of mass transport in the bulk whereas the latter relates to the mobility of the structural units on the crystal/liquid interface. We then employed the values of η(T) reduced by eightfold to calculate the growth rates U(T). The resultant U(T) curve is consistent with experimental data until the temperature decreases to a decoupling temperature T(d)(U) ≈ 1.1-1.2T(g), when D(eff)(η) begins decrease with decreasing temperature faster than D(eff)(U). A similar decoupling occurs between D(eff)(η) and D(eff)(τ) (estimated from nucleation time-lags) but at a lower temperatureT(d)(τ) ≈ T(g). For T > T(g) the values of D(eff)(τ) exceed D(eff)(η) only by twofold. The different behaviors of D(eff)(τ)(T) and D(eff)(U)(T) are likely caused by differences in the mechanisms of critical nuclei formation. Therefore, we have shown that at low undercoolings, viscosity data can be employed for quantitative analyses of crystal growth rates, but in the deeply supercooled liquid state, mass transport for crystal nucleation and growth are not controlled by viscosity. The origin of decoupling is assigned to spatially dynamic heterogeneity in glass-forming melts.     

Microviscosity in multiple regions of complex aqueous solutions of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)

Aqueous poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO109-PPO41-PEO109) copolymers are nonionic surfactants that self-organize to form aggregate structures with increasing temperature or concentration. We have studied two concentrations over a range of temperatures so that the copolymers are in one of three microphases: unimers, micelles, or hydrogels formed from body centered cubic aggregates of micelles. Three different coumarin dyes were chosen based on their hydrophobicity so that different aggregate regions could be probed independently-water insoluble coumarin 153 (C153), hydrophobic coumarin 102 (C102), and the hydrophilic sodium carboxylate form of coumarin 343 (C343-). Fluorescence anisotropy experiments provide detailed information on the local microviscosity. C153 experiences a fourfold increase in reorientation time and hence microviscosity with increasing temperature through the microphase transition from unimers to micelles. C102 also shows an increase in microviscosity with temperature but smaller in magnitude and with the microphase transition shifted to higher temperature relative to C153. C343- shows only a slight sensitivity to the microphase transition. For any of the three coumarin probes, fluorescence anisotropies do not show any correlation with the microphase transition to form cubic hydrogels.     

A femtosecond study of excitation wavelength dependence of solvation dynamics in a PEO-PPO-PEO triblock copolymer micelle

Excitation wavelength (lambdaex) dependence of solvation dynamics of coumarin 480 (C480) in the micellar core of a water soluble triblock copolymer, PEO20-PPO70-PEO20 (Pluronic P123), is studied by femtosecond and picosecond time resolved emission spectroscopies. In the P123 micelle, the width of the emission spectrum of C480 is found to be much larger than that in bulk water. This suggests that the P123 micelle is more heterogeneous than bulk water. The steady state emission maximum of C480 in P123 micelle shows a significant red edge excitation shift by 25 nm from 453 nm at lambdaex=345 nm to 478 nm at lambdaex=435 nm. The solvation dynamics in the interior of the triblock copolymer micelle is found to depend strongly on the excitation wavelength. The excitation wavelength dependence is ascribed to a wide distribution of locations of C480 molecules in the P123 micelle with two extreme environments-a bulklike peripheral region with very fast solvent response and a very slow core region. With increase in lambdaex, contribution of the bulklike region having an ultrafast component (< or =2 ps) increases from 7% at lambdaex=375 nm to 78% at lambda(ex)=425 nm while the contribution of the ultraslow component (4500 ps) decreases from 79% to 17%.     

Synthesis and reactivity of a transition metal complex containing exclusively TEMPO ligands: Ni(η2-TEMPO)2

The reaction of Ni(COD)(2) with two equivalents of the TEMPO radical at 68 °C affords the 16 e(-) "bow-tie" complex Ni(η(2)-TEMPO)(2), 1, in 78% yield. Compound 1 reacts with tert-butyl isocyanide and phenylacetylene at room temperature to yield the 16 e(-) distorted square planar nickel complexes Ni(η(2)-TEMPO)(η(1)-TEMPO)(CN(t)Bu), 2, and Ni(η(2)-TEMPO)(η(1)-TEMPOH)(CCPh), 4, respectively. The facile reactivity of 1 is aided by the transition of the TEMPO ligand from an η(2) to η(1) binding mode. Complex 4 is an unusual example of hydrogen atom transfer from phenylacetylene to a coordinated TEMPO ligand.     

Effect of electrostatic interaction on the location of molecular probe in polymer-surfactant supramolecular assembly: a solvent relaxation study

Effect of electrostatic interaction on the location of a solubilized molecular probe with ionic character in a supramolecular assembly composed of a triblock copolymer, P123 ((ethylene oxide) 20-(propylene oxide) 70-(ethylene oxide) 20) and a cosurfactant cetyltrimethylammonium chloride (CTAC) in aqueous medium has been studied using steady-state and time-resolved fluorescence measurements. Coumarin-343 dye in its anionic form has been used as the molecular probe. In the absence of the surfactant, CTAC, the probe C343 prefers to reside at the surface region of the P123 micelle, showing a relatively less dynamic Stokes' shift, as a large part of the Stokes' shift is missed in the present measurements due to faster solvent relaxation at micellar surface region. As the concentration of CTAC is increased in the solution, the percentage of the total dynamic Stokes' shift observed from time-resolved measurements gradually increases until it reaches a saturation value. Observed results have been rationalized on the basis of the mixed micellar structure of the supramolecular assembly, where the hydrocarbon chain of the CTAC surfactant dissolves into the nonpolar poly(propylene oxide) (PPO) core of the P123 micelle and the positively charged headgroup of CTAC resides at the interfacial region between the central PPO core and the surrounding hydrated poly(ethylene oxide) (PEO) shell or the corona region. The electrostatic attraction between the anionic probe molecule and the positively charged surface of the PPO core developed by the presence of CTAC results in a gradual shift of the probe in the deeper region of the micellar corona region with an increase in the CTAC concentration, as clearly manifested from the solvation dynamics results.     

P123重水溶液的物理凝胶化及凝胶结构

利用 1H NMR方法, 研究了高浓度的P123(PEO20PPO70PEO20)在重水溶液中的溶胶-凝胶转变过程. 升高温度使得体系发生溶胶-凝胶转变, 进一步升高温度, 体系发生凝胶-溶胶转变. 通过对不同质子基团的谱线宽度和化学位移偏移的分析, 同时结合流变学频率扫描和同步辐射(SR)研究, 发现质量分数为30%的P123的重水溶液在凝胶化过程中, 结构经历了由立方相(cubic)-六角柱状相(hcp)-层状相(lamellar)的转变过程, 其中立方相为面心立方(fcc)和六角密堆积球状相(hcps)的混合相. 高温时从凝胶到溶胶的转变主要体现为P123形成富集区与水发生相分离的过程.     

A femtosecond study of excitation wavelength dependence of a triblock copolymer-surfactant supramolecular assembly: (PEO)20-(PPO)70-(PEO)20 and CTAC

Solvation dynamics and anisotropy decay of coumarin 480 (C480) in a supramolecular assembly containing a triblock copolymer, PEO20-PPO70-PEO20 (Pluronic P123) and a surfactant, CTAC (cetyl trimethylammonium chloride) are studied by femtosecond up-conversion. In a P123-CTAC complex, C480 displays a significant (22 nm) red edge excitation shift (REES) in the emission maximum as lambda ex increases from 335 to 445 nm. This suggests that the P123-CTAC aggregate is quite heterogeneous. The average rotational relaxation time (tau rot) of C480 in a P123-CTAC complex decreases by a factor of 2 from 2500 ps at lambda ex = 375 nm to 1200 ps at lambda ex = 435 nm. For lambda ex = 375 nm, the probe molecules in the buried core region of P123-CTAC are excited and the solvation dynamics displays three components, 2, 60, and 4000 ps. It is argued that insertion of CTAC in P123 micelle affects the polymer chain dynamics, and this leads to reduction of the 130 ps component of P123 micelle to 60 ps in P123-CTAC. For lambda ex = 435 nm, which selects the peripheral highly polar corona region, solvation dynamics in P123-CTAC and P123 are extremely fast with a major component of <0.3 ps ( approximately 80%) and a 2 ps ( approximately 20%) component.     

C60-induced alkyne-alkyne coupling and alkyne scission reactions of a tungsten tris(diphenylacetylene) complex

Reaction of W(NCMe)(η(2)-PhC≡CPh)(3) with C(60) affords W(η(3)-NC(Me)C(60))(η(4),η(2)-C(6)Ph(6)) (2) and W(≡CPh)(NCMe)(η(2)-C(60)) (η(3),η(2)-C(5)Ph(5)) (3). The hexaphenylbenzene species of 2 shows an η(4)-butadiene + η(2)-olefin bonding mode and the nitrile carbon is inserted into one 6:5-ring junction of C(60). Compound 3 contains an η(3),η(2)-pentaphenylcyclopentadienyl and a benzylidyne group from 2 + 2 + 1 cyclization and scission reactions of the diphenylacetylene ligands.     

A reactive Ru-binaphtholate building block with self-tuning hapticity

A versatile Ru-BINO building block is reported, which offers a straightforward entry point into the chemistry of atropisomeric binaphtholate complexes of ruthenium. Reaction of RuCl(2)(PPh(3))(3)6a with Tl(2)((S)-BINO) affords Ru((S)-BINO)(PPh(3))(2)7 as a mixture of isomers: in 7', the BINO ligand is bound via η(3)-CCO,η(1)-O' donors, and in symmetrical 7″, via η(3)-CCO,η(3)-O'C'C' interactions. The bis(enolate) BINO bonding mode in the latter, not previously observed for any metal, underscores the remarkable geometric and electronic flexibility of the binaphtholate moiety. The BINO ligand proves able to stabilize complexes containing as few as two, and as many as four, additional ligands in 7 and its derivatives, enabling a synthetic versatility that contrasts with that of the superficially similar o-catecholate complex Ru(o-cat)(PPh(3))(3). As with the important achiral Ru precursor 6a, complex 7 undergoes facile transformation into a range of products under mild conditions, including acetonitrile, pyridine, and vinylidene derivatives. Single-crystal X-ray structures are reported for three of these complexes: Ru(η(3),η(3)-(S)-BINO)(PPh(3))(2)7″, Ru(η(3),η(1)-(S)-BINO)(PPh(3))(2)(MeCN) 9, and Ru(η(3),η(1)-(S)-BINO)(PPh(3))(py)(2)11. (13)C{(1)H} NMR signatures are proposed for new and known BINO coordination modes (η(1)-O,η(1)-O'; η(1)-C1,η(1)-O'; η(3)-CCO,η(3)-O'C'C'; η(3)-CCO,η(1)-O'; η(6)-C(6),η(1)-O'), as a potential aid to further developments in late-metal BINO chemistry.     

Theoretical investigation of the excited states of coumarin dyes for dye-sensitized solar cells

Using time-dependent density functional theory (TD-DFT), configuration interaction single (CIS) method, and approximate coupled cluster singles and doubles (CC2) method, we investigated the absorption spectra of coumarin derivative dyes (C343, NKX-2388, NKX-2311, NKX-2586, and NKX-2677), which have been synthesized for efficient dye-sensitized solar cells. The CC2 calculations are found in good agreement with the experimental results except for the smallest coumarin dye (C343). TD-DFT underestimates the vertical excitation energy of the larger coumarin dyes (NKX-2586 and -2677). Solvents (methanol) are found to induce a red shift of the vertical excitation energies, and their effects on the molecular geometry and the electronic structure are examined in detail. The deprotonated form of coumarin is also investigated, where a blue shift of the vertical excitation energies is observed.     

Quantitative SAXS analysis of the P123/water/ethanol ternary phase diagram

The ternary phase diagram of the amphiphilic triblock copolymer PEO-PPO-PEO ((EO)(20)(PO)(70)(EO)(20) commercialized under the generic name P123), water, and ethanol has been investigated at constant temperature (T = 23 degrees C) by small-angle X-ray scattering (SAXS). The microstructure resulting from the self-assembly of the PEO-PPO-PEO block copolymer varies from micelles in solution to various types of liquid crystalline phases such as cubic, 3D hexagonal close packed spheres (HCPS), 2D hexagonal, and lamellar when the concentration of the polymer is increased. In the isotropic liquid phase, the micellar structural parameters are obtained as a function of the water-ethanol ratio and block copolymer concentration by fitting the scattering data to a model involving core-shell form factor and a hard sphere structure factor of interaction. The micellar core, the aggregation number, and the hard sphere interaction radius decrease when increasing the ethanol/water ratio in the mixed solvent. We show that the fraction of ethanol present in the core is responsible for the swelling of the PPO blocks. In the different liquid crystalline phases, structural parameters such as lattice spacing, interfacial area of PEO block, and aggregation number are also evaluated. In addition to classical phases such as lamellar, 2D hexagonal, and liquid isotropic phases, we have observed a two-phase region in which cubic Fm3m and P6(3)mmc (hexagonally close packing of spheres (HCPS)) phases coexist. This appears at 30% (w/w) of P123 in pure water and with 5% (w/w) of ethanol. At 10% (w/w) ethanol, only the HCPS phase remains present.     

Probing Viscosity of Co-Polymer Hydrogel and HeLa Cell Using Fluorescent Gold Nanoclusters: Fluorescence Correlation Spectroscopy and Anisotropy Decay

Fluorescence dynamics of gold nanoclusters (Au₉ and Au₂₅) are studied in the complex and crowded environment of a triblock co-polymer (F127) hydrogel and inside cervical cancer cell, HeLa. In the hydrogel, spherical micelles of F127 remain immobilized with a hydrophobic core (PPO) and a hydrophilic corona (PEO) region. The fluorescence anisotropy decay suggests that the timescale of rotational relaxation in the hydrogel is similar to that in bulk water (viscosity ∼1 cP). From fluorescence correlation spectroscopy (FCS) it is inferred that the local viscosity in the hydrogel is 12 cP for Au₉ and 18 cP for Au₂₃. These results indicate that gold nanoclusters (AuNCs) localize in the corona region of the hydrogel. Evidently, frictions against rotation and translation are different inside the gel. It is suggested that rotation of the AuNCs senses the immediate water-like “void” region while translation motion involves in-and-out movement of the AuNCs at the periphery of the gel. Finally, the gold nanoclusters are used for cell imaging and estimation of intracellular viscosity of HeLa cells.     

Trinuclear, tetranuclear, and polymeric Cu(II) complexes from the first use of 2-pyridylcyanoxime in transition metal chemistry: synthetic, structural, and magnetic studies

The first use of 2-pyridylcyanoxime, (py)C(CN)NOH, in transition metal chemistry is described. Depending on the nature of the metal starting material and the reaction conditions employed, the Cu(II)/(py)C(CN)NOH system has provided access to complexes [Cu(3)O{(py)C(CN)NO}(3)(NO(3))(H(2)O)(2)(MeOH)] (1), [Cu(4)O{(py)C(CN)NO}(4)(O(2)CMe)(2)] (2), [Cu(4)(OH)(2){(py)C(CN)NO}(2)(O(2)CPh)(4)](2n)·n[Cu(4)(OH)(2){(py)C(CN)NO}(2)(O(2)CPh)(4)] (3), and [Cu{(py)C(CN)NO}(2)](n) (4). The molecule of 1 consists of three Cu(II) atoms in a strictly equilateral arrangement bridged by a central μ(3)-oxide group. The molecule of 2 consists of a tetrahedron of Cu(II) atoms held together by a central μ(4)-oxide ion, four η(1):η(1):η(1):μ-(py)C(CN)NO(-) ligands and two η(1):η(1):μ-MeCO(2)(-) groups. The crystal structure of 3 consists of [Cu(4)(OH)(2){(py)C(CN)NO}(2)(O(2)CPh)(4)](2n) double chains and discrete cluster [Cu(4)(OH)(2){(py)C(CN)NO}(2)(O(2)CPh)(4)] molecules. The crystal structure of 4 consists of neutral polymeric chains based on centrosymmetric mononuclear [Cu{(py)C(CN)NO}(2)] units. The Cu(II) atoms are doubly bridged by the oximate groups of two η(1):η(1):η(1):μ-(py)C(CN)NO(-) ligands. Variable-temperature, solid-state direct current (dc) magnetic susceptibility studies were carried out for 1-4. The data indicate very strong antiferromagnetic exchange interactions for 1-3. The obtained J values are discussed in depth on the basis of the structural parameters of the complexes, literature reports, and existing magnetostructural correlations.     

Host-Guest Interactions and Laser Activity in AlPO4-5/Laser Dye Composites

In situ inclusion of the laser dyes coumarin 466, coumarin 7, pyridine 2 and DCM has been conducted successfully in AlPO₄-5 crystals. The charged molecule pyridine 2 interacts with the framework and leads to bundle-like morphologies with increasing dye content. Uncharged molecules (DCM, coumarin 7, coumarin 466) are included, although corresponding molecular dimensions are exceeding pore size. These dyes probably induce local defects in the pore walls of AlPO₄-5 which are healed during crystal growth leading to well-developed hexagonal prisms. Spectroscopic studies show interactions of the dyes with the solid-state matrix which are reflected by shifts of absorption and emission maxima of the dyes. For the first time, laser activity is demonstrated on a perfect hexagonal single AlPO₄-5/DCM crystal.