On the formation of 2- and 3-cyanofurans and their protonated forms in interstellar medium conditions: quantum chemical evidence.

The literature is still poor in theoretical and experimental, including both spectroscopic and thermodynamic data for protonated furan and protonated 2-cyanofuran and 3-cyanofuran (FH+, 2CFH+ and 3CFH+). These data are, however, crucial for astrophysicists and astrochemists in the detection of new species in interstellar medium (ISM), the discovery of these molecular species being not yet reported. It is in this perspective that a computational study based on quantum chemistry on FH+, 2CFH+ and 3CFH+ was undertaken. A series of properties including the proton affinity (PA) of furan and the two cyanofurans, the variations of enthalpy (Δr H), entropy (Δr S), and Gibbs free energy (Δr G) for the reactions yielding cyanofurans (neutral and protonated forms), were studied at different temperatures (5 K, 10 K, 150 K and 298 K) and pressures (P = 1 atm and P = 10-5 atm) based on modern computational models (G2MP2, G3, G4MP2 and G4). While confirming that the protonation favors the α-position for furan, the PA values show that the protonation favors the nitrogen atom in cases of 2CFH+ and 3CFH+. The Δr H, Δr S and Δr G values revealed spontaneous reactions producing these species under ISM conditions of temperature and pressure. In addition quadrupole hyperfine structures and vibrational spectra which are essential tools for the characterization and the identification of interstellar molecular species are predicted, while the region where brightest lines fall for different temperatures is discussed. The results reported in this work are expected to assist astrophysicists and astrochemists, in the search for new chemical species in interstellar environments.

Judicious design functionalized 3D-COF to enhance CO2 adsorption and separation.

The effects of functional groups (including OH, OCH3 , NH2 , CH2 NH2 , COOH, SO3 H, OCO(CH2 )2 COOH(E-COOH), and (CH2 )4 COOH(c-COOH)) in 3D covalent organic frameworks (3D-COFs) on CO2 adsorption and separation are investigated by grand canonical Monte Carlo (GCMC) simulations and density functional theory calculations. The results indicate that interaction between CO2 and the framework is the main factor for determining CO2 uptakes at low pressure, while pore size becomes the decisive factor at high pressure. The binding energy of CO2 with functionalized linker is correlated to CO2 uptake at 0.3 bar and 298 K on 3D-COF-1, suggesting functional groups play a key role in CO2 capture in microporous 3D-COFs. Moreover, CO2 selectivity over CH4 , N2 , and H2 can be significantly enhanced by functionalization, where CH2 NH2 , COOH, SO3 H, and E-COOH enhance CO2 adsorption more effectively at 1 bar. Among them, SO3 H is the most promising functional group in 3D-COFs for CO2 separation.

Water-Robust Zinc-Organic Framework with Mixed Nodes and Its Handy Mixed-Matrix Membrane for Highly Effective Luminescent Detection of Fe3+, CrO42-, and Cr2O72- in Aqueous Solution.

Metal-organic frameworks (MOFs) and MOF-based composites as luminescent sensors with excellent economic practicability and handy operability have attracted much attention. Herein, we designed and fabricated a porous Zn-based MOF, [Zn(OBA)2(L1)·2DMA]n [1; H2OBA = 4,4'-oxybis(benzoic acid), L1 = 2,4,6-tris(4-pyridyl)pyridine, and DMA = N,N-dimethylacetamide], with mixed nodes under solvothermal conditions, and the pore size of 5.9 Å was calculated from N2 adsorption isotherms by using a density functional theory model. The as-synthesized compound 1 is stable in different boiling organic solvents and water solutions with a wide pH range of 2-12 and exhibits intense luminescence emission at 360 nm under excitation of 290 nm. Significantly, compound 1 shows high selective detection of Fe3+, CrO42-, and Cr2O72- in aqueous solution even under the interference of other ions. Compound 1 can quickly sense these ions in a short time and has a striking sensitivity toward Fe3+ with an ultralow limit of detection (LOD) of 1.06 µM. The relatively low LODs for CrO42- and Cr2O72- are 3.87 and 2.37 µM, respectively, compared to the reported works. Meanwhile, compound 1 can be reused to detect Fe3+, CrO42-, and Cr2O72- six times by simple regeneration. Considering the practicability, a mixed-matrix membrane (MMM) incorporated compound 1 and poly(methyl methacrylate) has been constructed. This MMM displays quick detection of Fe3+, CrO42-, and Cr2O72- and prompt regeneration by lifting from the analyte. This useful MMM shows a comparable LOD below 4.35 µM for these ions. This work presents a cost-effective Zn-based MOF as a functional platform for simple but useful sensing of Fe3+, CrO42-, and Cr2O72- in aqueous solution.

Theoretical investigation of protonated thiophene and two of its nitrile substituted derivatives (2-cyanothiophene and 3-cyanothiophene).

Theoretical and experimental spectroscopic data for protonated cyano-thiophenes (R-CNH+ with R = C4H3S), which are needed for their interstellar search and/or detection, are still lacking in the literature. Considering the high abundance and reactivity of H3+ in the interstellar medium (ISM), a quantum chemical investigation on protonated thiophene and two of its nitrile-substituted derivatives (2-cyanothiophene and 3-cyanothiophene) is undertaken for their characterization. The geometrical structures for the title species are calculated at the M06-2X/6-31G(d,p) level of theory, followed by an empirical correction for systematic errors. At the same level of theory, IR and Raman spectra are explored and the rotational parameters are calculated. The proton affinity (PA) of R-CN and the enthalpy, entropy and Gibbs free energy changes (ΔrH, ΔrS and ΔrG) of the reactions producing R-CNH+ are computed at the G2(MP2) and G3B3 levels of theory and at different temperatures. The PA calculations show that the protonation favors the nitrogen atom, while ΔrH, ΔrS, and ΔrG reveal the spontaneous reactions producing R-CNH+ and their neutral forms. In addition, quadrupole hyperfine structures are predicted, while the region where the brightest lines fall at different temperatures is discussed. These results are expected to assist astrophysicists and astrochemists in the search for new species in the ISM.

A Trinuclear Cobalt-Organic Framework: Solvatochromic Sensor towards CH2 Cl2 , and its Derivative as an Anode of Lithium-Ion Batteries with High Performance.

Here, a porous cobalt-organic framework with pillared layer structures, namely [Co3 OBA3 PTD(H2 O)2 ⋅ 2 DMA⋅H2 O]n (1, H2 OBA=4,4'-oxybis(benzoic acid); PTD=6-(pyridin-4-yl)-1,3,5-triazine-2,4-diamine), was fabricated by using cobalt trinuclear nodes, low-cost carboxylic linker, and accessible nitrogen heterocyclic ligands. This compound exhibited a highly efficient solvatochromism towards CH2 Cl2 within one minute and can be used 200 times at least. The corresponding dropper detector was assembled as a practical sensor. Meanwhile, the porous Co3 O4 was obtained by a simple but effective annealing treatment. Electrochemical measurements confirm that this Co3 O4 material derived from compound 1 shows high and stable lithium storage capabilities (1081.75 mA h g-1 at 200 mA g-1 after 115 cycles) and excellent rate properties.

Molecular structure, IR, Raman and UV-VIS spectra of 2-cyanothiophene and 3-cyanothiophene: A comparative quantum chemical investigation.

Spectroscopic data which are needed for detection of new species in the interstellar medium (ISM) are missing for five- and six-membered ring substituted derivatives. In order to supplement the existing literature information, quantum chemical calculations, including geometrical optimizations, simulated IR, Raman and UV-VIS spectra were carried out for 2-cyanothiophene (2CNT) and 3-cyanothiophene (3CNT). Structures for these molecular species were calculated from M06-2X/6-31G(d,p) computed results in conjunction with corrections for systematic deficiencies of basis sets and empirical adjustments for some geometrical parameters. A complete description of IR and Raman spectra including IR frequency assignment and potential energy distribution (PED) analysis is provided. IR and Raman spectra for deuterated species and UV-VIS spectra for thiophene, 2CNT and 3CNT were analyzed. The present computed molecular data are expected to assist astro-scientists in the search of these species in the ISM.

Chemical composition and oral toxicity assessment of Anisophyllea boehmii kernel oil: Potential source of new edible oil with high tocopherol content.

Anisophyllea boehmii is an indigenous and wild species in Burundi. Its fruits are edible and commercialized in local markets. This study investigates chemical quality, composition and toxicity test of A. boehmii kernel oil from two sites in eastern Burundi. Results of the present study reveal A. boehmii kernels to be an oil-rich source, yielding up to 29% of oil. Fatty acid composition analysis classifies these oils as palmitic. In fact, the main fatty acids are palmitic acid (36.47-39.55%) and oleic acid (18.83-22.21%). The analysis of minor compounds shows high tocopherols (485-657 mg kg-1), phenols (82-135 mg kg-1) and ß-carotene (144-234 mg kg-1) content. The physicochemical parameters analyzed make A. boehmii kernel a source of good quality oil. Furthermore, acute oral toxicity test reveals no toxicity of A. boehmii kernel oil. Results of the present study are decisive in adoption of A. boehmii kernel oil as an alternative source of edible oil.

Theoretical study on the influence of ancillary and cyclometalated ligands on the electronic structures and optoelectronic properties of heteroleptic iridium(III) complexes.

We report a theoretical analysis of a series of heteroleptic iridium(III) complexes (dox)(2)Ir(acac) [dox = 2,5-diphenyl-1,3,4-oxadiazolato-N,C(2), acac = acetylacetonate] (1a), (fox)(2)Ir(acac) [fox = 2,5-bis(4-fluorophenyl)-1,3,4-oxadiazolato-N,C(2)] (1b), (fox)(2)Ir(Et(2)dtc) [Et(2)dtc = N,N'-diethyldithiocarbamate] (2), (fox)(2)Ir(Et(2)dtp) [Et(2)dtp = O,O'-diethyldithiophosphate] (3), (pypz)(2)Ir(acac) [pypz = 3,5-di(2-pyridyl)pyrazole] (4a), (O-pypz)(2)Ir(acac) (4b), (S-pypz)(2)Ir(acac) (4c) and (bptz)(2)Ir(acac) [bptz = 3-tert-butyl-5-(2-pyridyl)triazole] (5) by using the density functional theory (DFT) method to investigate their electronic structures and photophysical properties and obtain further insights into the phosphorescent efficiency mechanism. Meanwhile, we also investigate the influence of ancillary and cyclometalated ligands on the properties of the above complexes. The results reveal that the nature of the ancillary ligands can influence the electron density distributions of frontier molecular orbitals and their energies, resulting in change in transition character and emission color, while the different cyclometalated ligands have a large impact on the charge transfer performances of the studied complexes. The calculated absorption and luminescence properties of the four complexes 1a, 1b, 2 and 3 are compared with the available experimental data and a good agreement is obtained. Further, the assumed complexes 4a and 4b possess better charge transfer abilities and more balanced charge transfer rates, and they are potential candidates as blue-emitting materials.

Combined effects of one 8-hydroxyquinoline/picolinate and "CH"/N substitutions on the geometry, electronic structure and optical properties of mer-Alq(3).

With the aim of evaluating the combined effect of one 8-hydroxyquinoline (q)/picolinate (p) and "CH"/N substitutions on the molecular geometry, electronic structure, and optical properties of tris-(8-hydroxyquinoline)aluminum [Alq(3)], the density functional theory (B3LYP) and time-dependent density functional theory (TD-B3LYP), using the 6-31G(d) and 3-21+G(d,p) basis sets were applied on Alq(3), Alq(2)p, and its "CH"/N-substitution derivatives. A comparison of the optimized ground-state (S(0)) geometries has shown that the molecular shape is conserved upon such a substitution. On the basis of the frontier molecular orbital and gap energy (E(g)) calculations, it was shown that, comparatively to the pristine Alq(2)p (and to the original parent Alq(3)), the HOMO and LUMO are stabilized, the net effect being an increasing or a decreasing E(g), depending on the position of the substituted group. The substitution of q(B) by p (from Alq(3) to Alq(2)p) was also found to induce the same feature. Starting from the S(0) and S(1) (first excited state) geometries, the effect of the substitution on the absorption (and emission) spectra was evaluated. It was found that the "CH"/N substitution in different positions on the two 8-hydroxyquinoline ligands may also constitute an efficient approach of tuning the Alq(2)p emitting color. In comparison with both Alq(3) and Alq(2)p, an important blue shift was predicted for the 5-substituted derivative, an important red shift being observed for the 4-substituted one. Also, relatively significant blue and red shifts were predicted for the 7- and 2-substituted derivatives. Finally, revisiting the correlation between the spectrum shifts and the metal-ligand bonding, our recent findings (2) were confirmed.

Design of an organic zeolite toward the selective adsorption of small molecules at the dispersion corrected density functional theory level.

Tris(o-phenylenedioxy)cyclotriphosphazene (TPP) became the compound of choice to investigate the structural features of organic zeolites and their potential applications as soft materials. A van der Waals crystal of the TPP analogue (host) with the thiophene side fragment tris(3,4-thiophenedioxy)cyclotriphosphazene (TTP) was designed to investigate the selective adsorption among some common gases (guest): methane (CH(4)), carbon dioxide (CO(2)), nitrogen (N(2)), or hydrogen (H(2)). The crystal structure of TTP was modeled by applying minimization methods using the COMPASS (condensed-phase optimized molecular potentials for atomic simulation studies) force field. Interaction energies and structural properties of van der Waals complexes of the crystal of TTP and gas molecules were studied using the dispersion corrected density functional theory (DFT-D). The proper functional and basis set were selected after comparing with benchmark data of the coupled-cluster calculations with singles, doubles, and perturbative triple excitations [CCSD(T)] estimated at the complete basis set (CBS) limit. On the basis of our results, the interaction energy between the host and the guest molecules was predicted in the increasing order of host-H(2) << host-N(2) < host-CH(4) < host-CO(2), suggesting the designed TTP is a good candidate as an organic zeolite for potential fuel storage, hydrogen purification, carbon dioxide removal from the air, as well as safety care in a coal mine.

Modulation of tris(o-phenylenedioxy)cyclotrisphosphazene (TPP) properties for zeolite use: effect of pi-conjugation length and CH/N heterosubstitution.

Highly accurate quantum chemical calculations were used in a comparative study of the pi-conjugation length and CH/N heterosubstitution effects on the structure and a number of properties of tris(o-phenylenedioxy)cyclotrisphosphazene (TPP) derivatives to identify the role of each of them in the modulation of the host...guest complex stability and available space for the adsorbate within TPP-like organic zeolite (OZ). From the BH&HLYP/6-31G(d,p) structures it was found that extending the side fragment with a phenyl ring and substituting CH/N preserve the "paddle wheel" molecular shape, a key factor in the tunnel formation on which the organic zeolite use of TPP is based on. Compared to the unsubstituted molecules, the side fragment is shortened for CH/N heterosubstitution, which may decrease the diameter of the tunnel. In addition, through accurate ionization potential (IP) calculations (at the HF/6-311+G(d) level) the electron-donor (E-D) capacity was found to be more significantly enhanced by a lateral than a linear extension with phenyl ring, while it decreased upon CH/N heterosubstitution, which can affect the stability of some related host...guest complexes in the same order. Finally, as recently reported for TPP, the current results based on PBE0/6-31G(d,p) show that upon release of an electron the structural stability may not be altered by a CH/N mono- or disubstitution. From these features it was concluded that if the crystal requirement can be attained clathrates of good tolerance toward guest molecules in a wide range of Lewis acidity with variable E-D strength and available space for adsorbates may be reasonably awaited by exploiting these two approaches.

Charge transport parameters and structural and electronic properties of octathio[8]circulene and its plate-like derivatives.

The first fully heterocyclic circulene very recently isolated, C(16)S(8), was studied by means of high accurate methods, allowing reliable predictions and interpretations of the structural and electronic properties of organic molecules bearing sulfur and selenium atoms. The changes induced by the oxidation process and the S/Se substitution on some of its properties and the infrared (IR) spectra were analyzed, allowing a comprehensive assignment of the bands observed in the case of C(16)S(8). The results confirmed the planarity and a large surface area of C(16)S(8), which remain in C(16)S(4)Se(4) and C(16)Se(4) derivatives, favoring their use for H(2) adsorption. The molecules were shown to have a strong aromatic character, while the IR spectrum of C(16)S(8) was elucidated, toward its possible application for a better understanding of the new class of materials; the IR signal associated to the asymmetric stretching of the CC bonds can be used as a structural signature to identify the neutral from the radical forms whose structural planarity was found to resist against the oxidation process. Some of the electronic and physical properties characterizing good electron-donating (ED) and charge-transporting (CT) capacity such as the frontier molecular orbital energies (E(HOMO), E(LUMO)), the ionization potential (IP), and the reorganization energy (lambda(h)/lambda(e) for hole/electron) were calculated and the influence of the cyclic structure of C(16)S(8) on them discussed. C(16)S(8), C(16)S(4)Se(4), and C(16)Se(4) were found to display a comparable/much lower lambda(h) and higher IP and E(LUMO) than those for some of the already well-known field-effect transistors (FET) materials such as pentacene, anthracene, and DT-TTF; further investigation for this issue is strongly recommended.

Shedding light on octathio[8]circulene and some of its plate-like derivatives.

A quantum chemical investigation is made on the recently synthesized octathio[8]circulene (C16S8), an exotic molecule, the first fully heterocyclic circulene, from the structural and electronic properties and some charge-transport parameters viewpoints. Since the molecule consists of eight thiophene rings fused together, we have chosen to compare it with the acyclic (octathienoacene) analogue and to some relatives thereof, in which the sulfur atoms are substituted by Se, NH, CH2 and O. C16S8, C16Se8 and C16S4Se4 are found to show a low reorganization energy comparable or lower than that for already well known field-effect transistor (FET) materials, a promising property which, combined to some others revealed by this study, makes these compounds potential candidates for FET use. In addition, the twist angle is found to be tightly linked to the peripheral bonds lengths, the least twisted structures showing the most interesting properties for organic FET use.

Optical properties of the phosphorescent trinuclear copper(I) complexes of pyrazolates: insights from theory.

Theoretical investigations have been performed to explore the optical properties of {[3,5-(CF3)(2)Pz]Cu}3 in monomeric and dimeric forms using TD-DFT approaches. The emission of all complexes originates from the lowest triplet excited-states (T1), and the corresponding emissive states are assigned as the mixture of the metal-centered charge transfer and ligand-to-metal charge transfer. The features of the emission spectrum are clarified in detail. The bulk emission spectrum of complex is mainly determined by the stacked dimers rather than the individual monomers. The predicted maximum emission wavelength (lambda(em)) are in good agreement with experimental values, indicating that the phosphorescence bands can be assigned to two different conformations for the neighboring stacked dimers sharing the same monomer in the complex. Energy transfer from T1 of one stacked dimer to the neighboring one is responsible for the disappearance of the shoulder, leaving only the main peak upon heating. With the aim to reveal the conformational dependence for the triplet excited-state emission spectrum, the optical properties of various stacked dimers with different conformations are investigated by varying the relative arrangements through changing inter-monomer distance or rotational angles for the dimer which is responsible for the main peak emission. Calculation results suggest that the shortest intermolecular Cu...Cu distance plays an important role in the emission spectra of the vertical- and tilting-movement dimers, which is ascribed to the variation of the energy gap for the frontier molecular orbitals involved in the main emitting transition. The blue shift of lambda(em) in parallel-movement and rotational dimers can be traced back to the variation of the mutual spatial orientation. Therefore, the modulation of the extent of movement or rotational angles for stacked dimers by external perturbations creates new possibilities for the design of molecular light-emitting devices.

Influence of the substituted side group on the molecular structure and electronic properties of TPP and related implications on organic zeolites use.

Tris(o-phenylenedioxy)cyclotriphosphazene (TPP) became a compound of choice to investigate the structural features of organic zeolite and their potential applications. Different TPP-like materials are studied in this Letter from the electron-donor (E-D) capacity viewpoint, since this was reported as a stabilizing parameter of the TPP-Lewis acid inclusion compound up to high temperatures. On the basis of DFT-PBE0/6-31G(d,p) calculations, the results reported herein show a tight dependence of the E-D of the entire molecule on that of the side group. It was shown that both the O/NH substitution and the extension of the phenylenedioxyl group with an aromatic ring significantly enhance the E-D. As a result, the corresponding clathrates, including some reported ones, may also be exploited for the same issue, with an even wider range of operating temperatures when trapping compounds of Lewis acidity character comparable to that of I2. Furthermore, it was concluded that these two strategies may significantly enhance the E-D capacity without altering the tolerance of TPP-like host materials to the guest molecules.

Theoretical study of unsymmetrical bisfullerene and its derivatives: C131, C129BN, and C130Si.

Unsymmetrical bisfullerene C(131) and its derivatives such as C(129)BN and C(130)Si are systematically investigated by semiempirical and density functional theory approaches. In comparison with the experimental data, calculated IR and NMR results reveal that both C(131)(H) and C(131)(P) isomers are possible compounds to coexist in the synthesized product. The C/Si and CC/BN substitution can change the electronic properties and reactivities compared with the pristine C(131)(H) and C(131)(P), respectively.

Design of TTF-based phosphazenes combining a good electron-donor capacity and possible inclusion adduct formation.

The physical properties of porous material can be modulated by intercalation of small molecules, whose size, in the case of tris-o-phenylenedioxy)cyclotriphosphazene (TPP)-based materials, vary with the different side groups. Starting from the TPP structure, a series of new derivatives were constructed through the core ring [(NP)(3)] substitution by [(CNH)(3)], [(CO)(3)], and [(CS)(3)] or/and the side group substitution by tetrathiafulvalene and a series of related fragments including bis(ethylenedithio)tetrathiafulvalene, 2-methylene-1, 3-dithiole, and 2-methylene-5,6-dihydro[1,3]dithiolo[4,5-b][1,4]dithiine. In the side fragment, such a substitution corresponds to the replacement of a ring heteroatom, an addition of substituents, or both. With use of theoretical methodologies based on DFT-B3LYP/6-31G* and HF/6-31G*//B3LYP/6-31G* approaches, molecular geometries and electronic properties including the LUMO and HOMO energies, the HOMO-LUMO gap, as well as the ionization potential (IP) were calculated. In comparison with the commonly used organic superconductors, most of the molecules investigated were predicted to show comparable or better electron-donor strength. Interestingly, a number of cyclophosphazene [(NP)(3)]-containing compounds were predicted to show the "paddle wheel" shape responsible for inclusion adducts formation, making these compounds to be potential candidates for organic superconductors with the ease of modulating their conducting properties by intercalation of suitable acceptors.

"CH"/N substituted mer-Gaq3 and mer-Alq3 derivatives: an effective approach for the tuning of emitting color.

Equilibrium geometry configurations of the "CH"/N substituted Alq3 and Gaq3 derivatives are calculated by density functional theory (B3LYP/6-31G). The frontier molecular orbital and gap energy calculations for all complexes have been performed at the HF/6-31G level. It was shown that, compared to the pristine molecules, the HOMO and LUMO are stabilized, the net effect being however an increasing/decreasing of the gap (Eg) depending on the position of the substituted group. On the basis of the equilibrium geometries, the effect of the substitution on the absorption and emission spectra was evaluated using TDB3LYP/3-21G. It was shown that the change of "CH"/N substituted position on 8-hydroxyquinoline ligand is a powerful approach for the tuning of emitting color. An important blue shift was predicted for 5-substituted 8-hydroxyquinoline derivatives, an important red one being observed for 4-substituted ones. Interestingly, relatively significant blue and red shifts were also predicted for the 7- and 2-substituted derivatives. In this work, the correlation between the spectrum shifts and the metal-ligand bonding is also discussed.