Weak Solvation Research Articles

Electron Solvation in Liquid Ammonia: Lithium, Sodium, Magnesium, and Calcium as Electron Sources.

A free electron in solution, known as a solvated electron, is the smallest possible anion. Alkali and alkaline earth atoms serve as electron donors in solvents that mediate outer-sphere electron transfer. We report herein ab initio molecular dynamics simulations of lithium, sodium, magnesium, and calcium in liquid ammonia at 250 K. By analyzing the electronic properties and the ionic and solvation structures and dynamics, we systematically characterize these metals as electron donors and ammonia molecules as electron acceptors. We show that the solvated metal strongly modifies the properties of its solvation shells and that the observed effect is metal-specific. Specifically, the radius and charge exhibit major impacts. The single solvated electron present in the alkali metal systems is distributed more uniformly among the solvent molecules of each metal's two solvation shells. In contrast, alkaline earth metals favor a less uniform distribution of the electron density. Alkali and alkaline earth atoms are coordinated by four and six NH3 molecules, respectively. The smaller atoms, Li and Mg, are stronger electron donors than Na and Ca. This result is surprising, as smaller atoms in a column of the periodic table have higher ionization potentials. However, it can be explained by stronger electron donor-acceptor interactions between the smaller atoms and the solvent molecules. The structure of the first solvation shell is sharpest for Mg, which has a large charge and a small radius. Solvation is weakest for Na, which has a small charge and a large radius. Weak solvation leads to rapid dynamics, as reflected in the diffusion coefficients of NH3 molecules of the first two solvation shells and the Na atom. The properties of the solvated electrons established in the present study are important for radiation chemistry, synthetic chemistry, condensed-matter charge transfer, and energy sources.

Understanding the thermosensitivity of POEGA-based star polymers: LCST-type transition in water vs. UCST-type transition in ethanol.

The lower critical solution temperature (LCST) transition in water and the upper critical solution temperature (UCST) transition in ethanol of poly(oligo(ethylene glycol) acrylate) (POEGA)-based core cross-linked star (CCS) polymers have been investigated and compared by employing turbidity, dynamic light scattering (DLS), (1)H NMR and FTIR measurements. Macroscopic phase transitions in water and in ethanol were observed to occur when passing through the transition temperature, as revealed by DLS and turbidity measurements. Analysis by IR indicated that the interactions between the polymer chains and solvent molecules in water are stronger than those in ethanol such that the CCS polymer arm chains in water adopt more extended conformations. Moreover, hydrophobic interaction among the aliphatic groups plays a predominant role in the LCST-type transition in water whereas weak solvation of the polymer chains results in the UCST-type transition in ethanol. Additionally, the LCST-type transition in water was observed to be much more abrupt and complete than the UCST-type transition in ethanol, as suggested by (1)H NMR and IR at the molecular level. Finally, an abnormal "forced hydration" phenomenon was observed during the LCST transition upon heating. This study provides a detailed understanding of the subtle distinctions between the thermal transitions of CCS polymers in two commonly used solvents, which may be useful to guide future materials design for a wide range of applications.

Complexation of Ni(ClO4)2 and Mg(ClO4)2 with 3-hydroxyflavone in acetonitrile medium: conductometric, spectroscopic, and quantum chemical investigation.

The complex formation of Ni(ClO4)2 and Mg(ClO4)2 with 3-hydroxyflavone (HL, flavonol) in acetonitrile was studied using conductometric and spectroscopic methods. It was found that interaction of nickel cation with HL leads to formation of the doubly charged [Ni(HL)](2+) complex, whereas in solutions of magnesium perchlorate the complex with anion [MgClO4(HL)](+) is formed. Using the extended Lee-Wheaton equation, the limiting equivalent conductivities of [Ni(HL)](2+) and [MgClO4(HL)](+) and thermodynamic constants of their formation were obtained at 288, 298, 308, 318, and 328 K. Calculated Stoke's radii indicate weak solvation of the formed complexes and low temperature stability of their solvation shells. On the basis of the quantum chemical calculations and noncovalent interactions analysis, it is found that in the solvated [Ni(HL)](2+) and [MgClO4(HL)](+) complexes interaction of the Ni(2+) and Mg(2+) cations with flavonol occurs via the carbonyl group of HL. Complexation with Ni(2+) does not change the internal structure of HL greatly: in the [Ni(HL)](2+) complex, flavonol shows an intramolecular H-bond between 3-hydroxyl and carbonyl groups. When a complex with [MgClO4](+) is formed, the OH group turns out of the plane of the chromone moiety that leads to rupture of an intramolecular H-bond in the ligand molecule. Moreover, in the [MgClO4(HL)](+) complex, perchlorate anion possesses a strong ability to interact with HL, forming an intracomplex H-bond between hydrogen of the 3-hydroxyl group and oxygen of ClO4(-). Its strength is more pronounced than in the intramolecular one in both [Ni(HL)](2+) and uncomplexed 3-hydroxyflavone.

Aqueous Sodium‐Ion Battery using a Na3V2(PO4)3 Electrode

AbstractThe NASICON‐type Na3V2(PO4)3 (NVP) cathode material is investigated in an aqueous sodium‐ion battery, which is explored by using a three‐electrode system. The battery behaviors and capacitive properties of this electrode system are critically investigated by using 1 m Li2SO4, Na2SO4, and K2SO4 electrolytes, with an optimal performance found to arise in Na+‐based electrolyte, which exhibits a capacitance of 209 Fg−1 at 8.5 C as well as enhanced ion diffusion. Larger, hydrated Li+ is less able to diffuse into the network of NVP, and the low conductivity and mobility leads to near noncapacitive behavior. In the case of K+‐based electrolyte, NVP presents asymmetric cyclic voltammograms, owing to weak solvation and the high conductivity of K+, making the ions more easily able to form electric double‐layer capacitance on the surface or pores of NVP, rather than insert into the network. The equivalent circuit based on electrochemical impedance spectroscopy result is analyzed to account for the electrochemical insertion behavior of Na+ into NVP, involving ion transfer in electrolyte solution, ion diffusion from the electrolyte to the electrode surface, as well as charge transfer and ion diffusion in the electrode solid.

Correlation between the standard Gibbs energies of an anion transfer from water to highly hydrophobic ionic liquids and to 1,2-dichloroethane

Cyclic voltammetry is used to investigate the transfer of several semihydrophobic and hydrophilic anions (F−, Cl−, Br−, I−, NO3-, NO2-, SCN−, BF4-, ClO4-, PF6-) across the polarized interface between an aqueous electrolyte solution and a highly hydrophobic ionic liquid (IL) membrane. Three ILs are examined being composed of the trioctadecylmethylammonium (TOMA+), tridodecylmethylammonium (TDMA+) or tetradodecylammonium (TDA+) cation and the tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (TFPB−) anion. The standard Gibbs energies of the anion transfer from water to IL, ΔGtr,i0,w→IL, are evaluated from the voltammetric measurements by applying the classical tetraphenylarsonium-tetraphenylborate hypothesis. Comparison of data for various ILs points to a small systematic effect of the cationic IL component, which is manifested by somewhat lower values of ΔGtr,i0,w→IL for most anions in the presence of TDMA+ or TDA+, indicating their stronger association with the anions. The capillary electrophoresis measurements suggest that the degree of interaction of anions with the IL cations in water could follow the order TDMA+ >TOMA+ >TDA+. It is shown that a linear correlation with the nearly unity slope between ΔGtr,i0,w→IL and the standard Gibbs energy of anion transfer from water to 1,2-dichloroethane (DCE), ΔGtr,i0,w→DCE, can be established for all three ILs studied. An extended correlation including both the present and the literature values of ΔGtr,i0,w→IL for the ion transfer from water to TDMATFPB reveals the consistency of data for the semihydrophobic cations and anions, and the presence of a weak solvation effect favoring the transfer of hydrophilic anions (F−, Cl−, Br−, I−) and disfavoring the transfer of hydrophilic cations (H+, Li+, Na+, K+, Rb+, Cs+).

Preferential Interactions between Lithium Chloride and Glucan Chains in N,N-Dimethylacetamide Drive Cellulose Dissolution

Naturally occurring cellulose is crystalline as a consequence of the strong interactions between the glucan chains that comprise it and therefore is insoluble in most solvents. One of the few solvent systems able to dissolve cellulose is lithium chloride (LiCl) dissolved in N,N-dimethylacetamide (DMA). By an integrated application of all-atom molecular dynamics (MD) simulations, reaction path optimization, free-energy calculations, and a force-matching analysis of coarse-grained atomistic simulations, we establish that DMA-mediated preferential interactions of Li(+) cations and Cl(-) anions with glucan chains enable cellulose dissolution in LiCl/DMA. The relatively weak solvation of Li(+), Cl(-), and glucan chains by DMA results in strong effective interactions of Li(+) and Cl(-) ions with the glucans, leading to cellulose dissolution. The small size of the Li(+) cations allows them to strongly couple to multiple interaction sites on the glucan chains of cellulose, including the spatially restricted regions around the ether linkages connecting neighboring glucose residues. Li(+) cations were thus identified as the main component responsible for driving cellulose dissolution. The mechanism for explaining the solubility of cellulose in the LiCl/DMA system deduced from the analysis of atomistic-scale simulations conducted in this work is also consistent with most of the empirical observations related to cellulose dissolution in salt/amide solvent systems.

Energetics and Structure of Uranium(VI)–Acetate Complexes in Dimethyl Sulfoxide

The thermodynamics of the complexation between uranium(VI) and acetate in dimethyl sulfoxide (DMSO) was studied at 298 K in an ionic medium of 0.1 mol dm(-3) tetrabutyl ammonium perchlorate. The results show that the uranyl ion forms three strong successive mononuclear complexes with acetate. The complexes, both enthalpically and entropically stabilized, are significantly more stable in DMSO than in water. This feature can be ascribed to the weak solvation of acetate in DMSO. The thermodynamic parameters for the formation of the uranium(VI) complexes with acetate in DMSO are compared with those with ethylenediamine in the same solvent. The difference between the two ligand systems reveals that, for the complexation reactions involving charge neutralization, the reorganization of the solvent gives a very important contribution to the overall complexation energetics. The coordination mode of acetate in the uranyl complexes and the changes of the solvation sphere of UO(2)(2+) upon complexation were investigated by FT-IR spectroscopy in DMSO and in acetonitrile/DMSO mixtures. In addition, DFT calculations were performed to provide an accurate description of the complexation at the molecular level. The experimental and calculated results suggest that acetate is solely bidentate to UO(2)(2+) in the 1:1 and 1:3 complexes but mono- and bidentate in the 1:2 complexes. The DFT calculations also indicate that the medium effects must always be taken into account in order to gain accurate information on the complex formation in solution. In fact, the relative stability of the reaction products changes markedly when the DFT calculations are carried out in vacuum or in DMSO solution.

Stereochemistry and Solvent Role in Protein Folding: Nuclear Magnetic Resonance and Molecular Dynamics Studies of Poly-l and Alternating-l,d Homopolypeptides in Dimethyl Sulfoxide

The competing interactions folding and unfolding protein structure remain obscure. Using homopolypeptides, we ask if poly-L structure may have a role. We mutate the structure to alternating-L,D stereochemistry and substitute water as the fold-promoting solvent with methanol and dimethyl sulfoxide (DMSO) as the fold-denaturing solvents. Circular dichroism and molecular dynamics established previously that, while both isomers were folded in water, the poly-L isomer was unfolded and alternating-L,D isomer folded in methanol. Nuclear magnetic resonance and molecular dynamics establish now that both isomers are unfolded in DMSO. We calculated energetics of folding-unfolding equilibrium with water and methanol as solvents. We have now calculated interactions of unfolded polypeptide structures with DMSO as solvent. Methanol was found to unfold and water fold poly-L structure as a dielectric. DMSO has now been found to unfold both poly-L and alternating-L,D structures by strong solvation of peptides to disrupt their hydrogen bonds. Accordingly, we propose that while linked peptides fold protein structure with hydrogen bonds they unfold the structure electrostatically due to the stereochemical effect of the poly-L structure. Protein folding to ordering of peptide hydrogen bonds with water as canonical solvent may thus involve two specific and independent solvent effects-one, strong screening of electrostatics of poly-L linked peptides, and two, weak dipolar solvation of peptides. Correspondingly, protein denaturation may involve two independent solvent effects-one, weak dielectric to unfold poly-L structure electrostatically, and two, strong polarity to disrupt peptide hydrogen bonds by solvation of peptides.

Correlation of the Rates of Solvolysis of Neopentyl Chloroformate—A Recommended Protecting Agent

The specific rates of solvolysis of neopentyl chloroformate (1) have been determined in 21 pure and binary solvents at 45.0 °C. In most solvents the values are essentially identical to those for ethyl and n-propyl chloroformates. However, in aqueous-1,1,1,3,3,3-hexafluoro-2-propanol mixtures (HFIP) rich in fluoroalcohol, 1 solvolyses appreciably faster than the other two substrates. Linear free energy relationship (LFER) comparison of the specific rates of solvolysis of 1 with those for phenyl chloroformate and those for n-propyl chloroformate are helpful in the mechanistic considerations, as is also the treatment in terms of the Extended Grunwald-Winstein equation. It is proposed that the faster reaction for 1 in HFIP rich solvents is due to the influence of a 1,2-methyl shift, leading to a tertiary alkyl cation, outweighing the only weak nucleophilic solvation of the cation possible in these low nucleophilicity solvents.

Solvation effect on the ion exchange in polypyrrole film doped with sulfonated polyaniline

Solvation effects on ion exchange of conducting polymer, polypyrrole (PPy), films, electrodeposited in a mixture consisting of conducting polymer, poly(2-methoxyaniline-5-sulfonate) (PMAS) as a polyanion additive and dodecylbenzene sulfonic acid (DBS) as main supporting electrolyte, were investigated by means of the volume change of the film. PMAS incorporation into PPy film was found to show large water content, indicating that the PMAS incorporation increases porosity in PPy film. Dynamic volume change in the film with redox reaction was found to be influenced by both of the nature of solvent as well as supporting electrolyte. Solvents with small donor and small acceptor number were found to display cathodic and anodic film expansions, respectively. Charge screening effect by weak solvation probably decreases the interaction between dopant ions and PPy, promoting the reversible volume change of the film due to facile ion exchange during the redox process. The magnitude of film deformation has also been assigned to the exchange of substantial particles having a same order of Stokes radius.

Adiabatic compressibility of tetraethylammonium tetrafluoroborate solutions in propylene carbonate

The density and ultrasound propagation velocity for Et4NBF4 solutions in propylene carbonate were determined in a concentration range of 0.01–0.8 mol/kg at 283.15, 298.15, and 308.15 K. Apparent molar compressibilities and volumes of the studied electrolyte in solvent were calculated. Solvation numbers and molar adiabatic compressibilities of solvate complexes were determined using the isoentropic compression method. These quantities indicated weak solvation of tetraethylammonium tetrafluoroborate in propylene carbonate in the range of concentrations practically used in ionistors.

Solution structure determination of tetranuclear platinum(II) cluster complex in acetic acid: X-ray diffraction and molecular dynamics simulation study

X-ray diffraction and molecular dynamics simulation studies were performed in order to describe the structure of [Pt(CH 3COO) 2] 4 complex in acetic acid. Structural information about the solution, the solvated complex, further on the often-neglected complex–solvent interactions in solution are discussed. Finally the change in the bulk structure of the solvent due to the presence of a complex solvate was also studied. The good agreement between the diffraction experiments and the results of molecular dynamics simulations justify the use of simulations in order to obtain a detailed description of the liquid structure by using partial radial distribution functions and hydrogen bond statistics. Acetic acid is described as a strong hydrogen bonding liquid, where the molecules mainly form a chain structure by hydrogen bonds but cyclic structures can also be identified. The bulk structure of the solution is only slightly affected by the solvation of the complex. On the basis of bonding and nonbonding Pt⋯Pt interactions obtained from X-ray diffraction results it can be stated that the [Pt(CH 3COO) 2] 4 complex maintains its shape in solution. An analysis of complex–solvent intermolecular interaction showed that only a very weak and diffuse solvation sphere is formed around the solvated complex.

Extended spin-boson model for nonadiabatic hydrogen tunneling in the condensed phase

A nonadiabatic rate expression for hydrogen tunneling reactions in the condensed phase is derived for a model system described by a modified spin-boson Hamiltonian with a tunneling matrix element exponentially dependent on the hydrogen donor-acceptor distance. In this model, the two-level system representing the localized hydrogen vibrational states is linearly coupled to the donor-acceptor vibrational mode and the harmonic bath. The Hamiltonian also includes bilinear coupling between the donor-acceptor mode and the bath oscillators. This coupling provides a mechanism for energy exchange between the two-level system and the bath through the donor-acceptor mode, thereby facilitating convergence of the time integral of the probability flux correlation function for the case of weak coupling between the two-level system and the bath. The dependence of the rate constant on the model parameters and the temperature is analyzed in various regimes. Anomalous behavior of the rate constant is observed in the weak solvation regime for model systems that lack an effective mechanism for energy exchange between the two-level system and the bath. This theoretical formulation is applicable to a wide range of chemical and biological processes, including neutral hydrogen transfer reactions with small solvent reorganization energies.

Preferential solvation of some copper (I), silver (I) and sodium (I) salts in acetonitrile + n-butyronitrile and acetonitrile + N, N-dimethylacetamide mixtures

Viscosities and densities of Bu 4NBPh 4, Bu 4NClO 4, Bu 4NI, Bu 4NBr, Pr 4NBr, Et 4NI, Et 4NBPh 4, CuClO 4, NaClO 4 and NaBPh 4 in AN + n-BTN and those of Bu 4NBPh 4, Bu 4NClO 4, Bu 4NCF 3COO, AgCF 3COO and CuClO 4 in AN + DMA mixtures in the concentration range (3–580) × 10 − 4 mol dm − 3 containing 100, 80, 60, 40, 20 and 0 mol% AN have been measured at 298 K. The viscosity data have been analyzed using the Jones–Dole equation in the form: η η o = 1 + A C 1 / 2 + B ⁢ C for unassociated and in the form η η o = 1 + A ( C ⁢ α ) 1 2 + B ( C ⁢ α ) + B ′ ( 1 − α ) C for associated electrolytes. The A-coefficients of the Jones–Dole equation are positive and are in reasonably good agreement with the limiting theoretical values ( A η ) calculated using Falkenhagen–Vernon equation in some cases and two to three times larger in other cases. The B coefficients of the electrolytes are positive and large in all cases. The ionic B + and B − coefficients have been evaluated from the B − coefficients of the electrolytes using a method reported by Gill and Sharma. The derived results show a strong preferential solvation of Na + and Cu + by n-BTN in AN + n-BTN and that of Ag + and Cu + by DMA in AN + DMA mixtures. Br −, I − and ClO 4 − show weak preferential solvation by the same solvents while CF 3COO − shows no preferential solvation in AN +DMA mixtures.

Correlation of PEO conformations and solvation in PEO–NaSCN polymer electrolytes

The polymeric conformations can provide insight into the structure and the mechanism of ion transport in solid polymer electrolytes. In this work, the FT-IR spectra of PEO–NaSCN complexes were measured at room temperature, and the solvation of NaSCN in PEO was revealed by the conformational changes of PEO with NaSCN content. It is suggested that the complexation of PEO with NaSCN can occur through three modes: trans-coordination, gauche-coordination, and cryptande-coordination, depending on the conformation and the flexibility of PEO backbone. The trans-coordination is a weak solvation and can cause the interchain crosslinking and the reduction of segmental motion. The gauche-coordination is a strong complexation and can form complexes in which Na + is wrapped by the PEO helix. The cryptandes result from the internal rotation of the flexible PEO backbone and can interact directly with NaSCN to form triple ion aggregations, especially when the salt content is low in PEO. In addition, the effect of PEO crystallinity on solvation and the solvating ability of PEO with different molecular weight are discussed also in this paper.

Solvent conformation and ion solvation: From molecular to ionic liquids

Abstract Metal ions are solvated in solution, and, in a sterically congested organic solvent, those solvent molecules that are simultaneously bound to the metal ion will be subject to consequential steric interactions through space. The molecular structure of a solvent, particularly that of any functional groups in the vicinity of the coordinating atom to the metal ion, plays a key role in the solvation steric effect. Weak solvation steric effects lead to a distorted octahedral structure for six-coordinate transition-metal(II) ions, whereas strong steric effects lead to a decreased solvation number. In particular cases, the conformation of a solvent may undergo a change in response to coordination to the metal ion. Solvation steric effects play a decisive role in reaction thermodynamics and kinetics of the metal ion. Here, we show our recent results on solvation steric effects in terms of structure and thermodynamics, particularly, the conformational change of solvent and its effect on the metal-ion complexation.

Stabilization of carbon dioxide-in-water emulsions with silica nanoparticles.

Stable carbon dioxide-in-water emulsions were formed with silica nanoparticles adsorbed at the interface. The emulsion stability and droplet size were characterized with optical microscopy, turbidimetry, and measurements of creaming rates. The increase in the emulsion stability as the silica particle hydrophilicity was decreased from 100% SiOH to 76% SiOH is described in terms of the contact angles and the resulting energies of attachment for the silica particles at the water-CO(2) interface. The emulsion stability also increased with an increase in the particle concentration, CO(2) density, and shear rate. The dominant destabilization mechanism was creaming, whereas flocculation, coalescence, and Ostwald ripening played only a minor role over the CO(2) densities investigated. The ability to stabilize these emulsions with solid particles at CO(2) densities as low as 0.739 g/mL is particularly relevant in practical applications, given the difficulty in stabilizing these emulsions with surfactants, because of the unusually weak solvation of the surfactant tails by CO(2).

Direct Measurement of the Fast, Reversible Addition of Oxygen to Cyclohexadienyl Radicals in Nonpolar Solvents

The title reaction was measured directly by laser flash photolysis in several nonpolar solvents, using both the strong ultraviolet and weaker visible absorption bands of the cyclohexadienyl radical. Both the visible and ultraviolet transient absorptions are shown to have identical time dependence, confirming that both absorptions correspond to the same species. The cyclohexadienyl radical's spectra were observed in several nonpolar solvents and are reported. The rate constant of the title reaction is 1.2 ± 0.4 × 109 M-1 s-1 in cyclohexane solvent at room temperature (298 K). This reaction is diffusion-limited, which is consistent with previous literature reports, but 2 orders of magnitude faster than the rate constant measured recently in the gas phase. Reasons for the discrepancy are explored, with the most likely explanation being that the title reaction becomes equilibrated in both the liquid and gas phases. Calculations reveal that the weak solvation of the nonpolar solvents coupled with higher oxygen...

Isentropic compressibilities of some copper(I), sodium(I) and tetraalkylammonium salts evaluated from ultrasonic velocity measurements in acetonitrile + N,N-dimethylformamide mixtures at 298.15 K

Ultrasonic velocity (u) and density (p) of tetrabutylammonium tetraphenylborate (Bu 4 NBPh 4 ), tetrabutylammonium perchlorate (Bu 4 NClO 4 ), copper(I) perchlorate tetraacetonitrile (CuClO 4 .4CH 3 CN), sodium perchlorate (NaClO 4 ) and sodium tetraphenylborate (NaBPh 4 ) have been measured at different salt concentrations in the concentration range 0.02-0.6 mol kg - 1 in binary mixtures of acetonitrile (AN) with N,N-dimethylformamide (DMF) containing 0, 10, 20, 40, 60, 75, 80, 90 and 100 mol % DMF. The isentropic compressibility (K s ) and apparent molal isentropic compressibility (K s , Φ ) of the salts in various solvent mixtures have been calculated. Limiting apparent molal isentropic compressibilities (K o s,Φ) for various salts have been evaluated and split into contributions of individual ions i.e. into (K o s,Φ) ′ values. The variation of (K o s,Φ) ′ values with solvent composition shows that Na + has very large negative (K o s,Φ) ′ values which show strong solvation of Na + in AN + DMF mixtures over the entire solvent composition range and the solvation of Na + by DMF is relatively stronger than that with AN. Cu + also shows strong but relatively less solvation as compared to Na + in AN + DMF mixtures over the entire solvent composition range. The solvation of Cu + by AN is relatively stronger than with DMF. ClO - 4 shows much weaker solvation in AN+DMF mixtures by having some interaction with AN in the AN rich region of the mixture.

A novel hyperbranched conjugated polymer for electroluminescence application

A novel hyperbranched conjugated polymer composed of 1,3,5-trivinylicbenzene cores and (2,5-dimethoxyl)-1,4-phenylenevinylene connecting units (HB2) was synthesized via Wittig reaction route. The resulting polymer has good solubility in common organic solvents due to its weak intermolecular interaction and low solvation energy. PL and EL properties of HB2 were inspected. In film, absorption of HB2 was slightly blue shifted from absorption in solution while PL emission was red shifted from that of solution. These marked differences suggested a large change in inter- and/or intra-molecular interaction from solution to solid film. Single layer light emitting diodes were fabricated utilizing HB2 as the emitting layer. Dispersing HB2 into a PVK matrix caused significant changes in the device performance. Bright blue emission >800cd/m2 can be achieved at a bias of 24V for the ITO/PVK:HB2=5:1/Ca/Al devices and efficiency of the polymer blend devices was an order of magnitude higher than that of the HB2 single layer devices.