Exploring the electro‐optical properties of conjugated polymers based on oligo‐selenophene and oligo(3,4‐ethylenedioxyselenophene)

For seeking high‐efficiency narrow‐band‐gap donor materials to enhance short‐circuit current density for organic solar cells, a series of oligo‐selenophene (OS) and oligo(3,4‐ethylenedioxyselenophene) (OEDOS) with various chain lengths were designed and characterized using density functional theory (DFT) and time‐dependent DFT calculations. Based on the results, it can be seen that with increasing chain length of the oligomers in both syn‐ and anti‐adding manners, the bond length alternation is decreased which indicates that the π‐electron delocalization is increased. Also, when the chain length is increased the electronic energy gap and the optical energy gap are decreased. It can be concluded that the syn‐(OS)_n=10,14,15, anti‐(OS)_n=14 and anti‐(OEDOS)_n=7–12 oligomers can act as low‐band‐gap polymers. Therefore they can absorb more sunlight based on maximum wavelength (higher than 620 nm). Furthermore, a red shift in the simulated absorption spectra of (OS)_n and (OEDOS)_n donors is observed. It is found that (OS)_n=14,15 with syn configuration of the extended oligomers is the most suitable donor for the design of high‐performance organic solar cells possessing a narrow electronic band gap, high exciton lifetime and broad and intense absorption spectra that cover the solar spectrum leading to complete light‐harvesting efficiency.     

Quantum chemical study of the host-guest inclusion complexes of the local anaesthetic drugs, procaine hydrochloride and butacaine hydrochloride, with α- and β-cyclodextrins

Quantum mechanical (QM) calculations were carried out in order to study the host-guest inclusion complexes of procaine hydrochloride (Pro-H) and butacaine hydrochloride (But-H) with α- and β-cyclodextrins (α- and β-CDs) by PM3 and AM1 methods. The systems were studied by a 1:1 (α-CD/Pro-H, α-CD/But-H, β-CD/Pro-H, and β-CD/But-H) stoichiometric ratio. In this work we calculated the energy of complex formation in vacuo, and this investigation was carried out on the basis of the host-guest approach. The stabilization energy results for the 1:1 host-guest inclusion complexes indicate that the β-CD/Pro-H complex is more stable than the α-CD/Pro-H complex. Furthermore, stabilization energy for the 1:1 inclusion complex of α-CD with But-H is lower than that for the 1:1 inclusion complex of β-CD with But-H. The calculation results show that all complexation processes for the four complexes are exothermic. Enthalpy changes for the α-CD/But-H and β-CD/Pro-H host-guest inclusion complexes are more negative than those for the other ones. ΔG ^o values for both the β-CD/Pro-H and α-CD/But-H complexes are negative. Correspondence: S. M. Hashemianzadeh, Department of Physical Chemistry, College of Chemistry, Iran University of Science and Technology, Tehran, Iran.     

Synthesis of new phosphorus ylides: Spectroscopic and X‐ray structural studies

Stable phosphoranes, Ar₃P = CHCOR (R = C₆H₅, C₆H₄NO₂, C₆H₄OCH₃, CH₃, OCH₂C₆H₅; Ar = p‐tolyl or phenyl), have been C‐acylated by acetic anhydride to obtain new types of phosphorus ylides. Synthesis and characterization of six phosphorus ylides of the type Ar₃PC(COCH₃)(COR) are reported. The reaction of {(p‐tolyl)₃PCHCOC₆H₅} ( I ), {(p‐ tolyl)₃PCHCOC₆H₄NO₂} ( II ), {Ph₃PCHCOC₆H₄NO₂} ( III ), {Ph₃PCHCOC₆H₄OCH₃} ( IV ), {(p‐tolyl)₃PCHCOCH₃} ( V ), and {Ph₃PCHCOOCH₂C₆H₅} ( VI ) with acetic anhydride in dry chloroform as solvent gives (p‐tolyl)₃PC(COMe)(COC₆H₅), α‐acetyl‐α‐benzoylmethy‐lenetriphenylphosphorane ( 1 ), {(p‐tolyl)₃PC(COMe) (COC₆H₄NO₂)} ( 2 ), {Ph₃PC(COMe)(COC₆H₄NO₂)} ( 3 ), {Ph₃PC(COMe)(COC₆H₄OCH₃)} ( 4 ), {(p‐tolyl)₃ PC(COCH₃)₂} ( 5 ), and {Ph₃PC(COMe)(COOCH₂ C₆H₅)} ( 6 ). Single crystal X‐ray analyses for ylides 2 , 5 , and 6 reveal the monoclinic ( 2, 5 ) and triclinic ( 6 ) crystal systems. Characterization of the obtained compounds was also performed by elemental analysis, IR, ¹H, ³¹P, and ¹³C NMR. The geometries of these compounds have been investigated using density functional theory (DFT). In addition, electronic parameters of these compounds such as HOMO and LUMO energy, Mulliken partial charge, and dipole moment were obtained. In this paper, the reactivity of these ylides is discussed in regard to the aforementioned data. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:475–485, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20633     

Theoretical prediction of encapsulation and adsorption of platinum-anticancer drugs into single walled boron nitride and carbon nanotubes

In this research, the adsorption and encapsulation of cisplatin, nedplatin, oxaliplatin and carbaplatin as Pt-anticancer drugs into the (7,7) boron nitride nanotube (BNNT) and carbon nanotube (CNT) are investigated using density functional theory. The different orientation modes of drug molecules onto the outer and inner surfaces of BNNT and CNT are studied. Analysis of the adsorption energy reveals that the complex formation process is favorable. The calculated adsorption energies indicate that the encapsulation of drugs inside the nanotubes is more favorable than the adsorption of drugs outside of the nanotubes. On the other hand, the results show that the BNNT/oxaliplatin(in) system is more stable than the others. The stabilization of nanotube/drug complexes results in electronic and structural properties change in the nanotubes. The natural bond orbital calculations show that the van der Waals forces, hydrogen bonding and electrostatic interactions are the major factors contributed to the overall stabilities of the complexes. The predicted electronic and structural properties of BNNT compared to the CNT towards Pt-anticancer drugs, suggest that BNNT can act as drug delivery vehicles.     

Canonical Monte Carlo simulation of adsorption of O2 and N2 mixture on single walled carbon nanotube at different temperatures and pressures

Adsorption of pure and mixtures of O₂ and N₂ on isolated single‐walled carbon nanotube (SWCNT) have been investigated at the subcritical (77 K) and different supercritical (273, 293, and 313K) temperatures for the pressure range between 1 and 31 MPa using (N,V,T) Monte Carlo simulation. Both O₂ and N₂ gravimetric storage capacity exhibit similar behaviors, gas adsorption is higher on outer surface of tube, compared to the inner surface. Results are consistent with the experimental adsorption measurements. All adsorption isotherms for pure and mixture of O₂ and N₂ are characterized by type I (Langmuir shape), indicating enhanced solid‐fluid interactions. Comparative studies reveal that, under identical conditions, O₂ adsorption is higher than N₂ adsorption, due to the adsorbate structure. Excess amount of O₂ and N₂ adsorption reach to a maximum at each temperature and specified pressure which can be suggested an optimum pressure for O₂ and N₂ storage. In addition, adsorptions of O₂ and N₂ mixtures have been investigated in two different compositions: (i) an equimolar gas mixture and (ii) air composition. Also, selectivity of nanotube to adsorption of O₂ and N₂ gases has been calculated for air composition at ambient condition. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Thermodynamic studies of inclusion complex formation between alkylpyridinium chlorides and β-cyclodextrin using conductometric method

Thermodynamics on inclusion complexation of β-cyclodextrin (β-CD) with n-alkylpyridinium chlorides (C _n PC, n = 12, 14, 16) were measured by conductivity technique to evaluate the effects of chain length of C _n PC and temperature. The data obtained indicate that inclusion complexes S(CD) and S(CD)₂ had formed between surfactant and β-CD in aqueous solution. Investigation showed that the K ₁ (first equilibrium constant) for S(CD) formation is greater than K ₂ (second equilibrium constant) for S(CD)₂ formation. It has been found that C₁₂PC forms only the 1:1 complex, while C₁₄PC and C₁₆PC form 1:1 and 1:2 complexes. Thermodynamic parameters of the complexation, i.e. ΔG°, ΔH° and ΔS° have been also calculated. The large values of ΔG° indicate that complexation between surfactant and β-CD is very favorable.