Studies on tetraborane(8) carbonyl, B4H8·CO: its isomeric composition in the gas phase and in solution, and its reactions with alkenes

¹¹B NMR spectra of tetraborane(8) carbonyl, B₄H₈·CO 1, reveal a changeover in the distribution of isomers in going from toluene solution to the gas phase. Fortuitously the distribution is 60:40 in each case, but comparison with published electron diffraction data and ab initio/IGLO computations indicates that the CO group is disposed endo with respect to the B₄ `butterfly' framework in the predominant isomer in the gas phase, and exo in solution. The results also allow conclusions to be drawn about the geometries of other B₄H₈·L isomers on the basis of their reported proton NMR chemical shifts. Reactions of B₄H₈·CO with ethene and propene at ca. 30 bar yield products, R₄B₄H₄·CO (R=Et 2 or Pr³ 3), in which all four wingtip hydrogen atoms of the tetraborane carbonyl have been replaced by alkyl groups. Variable-temperature ¹¹B and ¹H NMR spectra of 2 and 3 reveal interesting fluxional behaviour.     

Preparation and surface photoelectric properties of Fe(II/III) complexes

Four Fe(II/III) supramolecules, {[Fe(Hpdc)₂(H₂O)₂]·2H₂O} (1), [Fe(HImbc)₂(H₂O)₂] (2), [Fe(phen)₂(CN)₂]·CH₃CH₂OH·2H₂O (3), K[Fe(tp)₂]·SO₄ (4) (H₂pdc = 2,5-Pyridinedicarboxylic acid, H₂Imbc = 4,5-Imidazoledicarboxylic acid, phen = 1,10-phenanthroline, tp⁻ = poly(pyrazolyl)borate), were synthesized by hydrothermal and room temperature stirring methods. They were characterized by single crystal X-ray diffraction, surface photovoltage spectroscopy (SPS), field-induced surface photovoltage spectroscopy (FISPS), electron paramagnetic resonance (EPR), UV–Vis absorption spectra (UV–Vis), infrared spectra (IR) and element analysis. The structural analyses indicate that complex (1) is a supramolecule with 2D structure connected by hydrogen bonds. Complex (2) is a supramolecule with hydrogen-bonded 3D structure. Complexes (3) and (4) are both 1D supramolecules connected by hydrogen bonds. The electronic state of central metal Fe(II) ions in complexes (1) and (2) is d⁶ with FeN₂O₄ coordination mode, lying in weaker distorted octahedral field. The electronic state of Fe(II) ion in complex (3) is d⁶ with Fe(CN)₂N₄ mode in the strong distorted octahedral field. The electronic state of Fe(III) ion in complex (4) is d⁵ with FeN₆ mode, lying in the strong octahedral field. The micro-environment of Fe(II/III) ions in the four complexes is further investigated by EPR. The SPS of four complexes all exhibit photovoltage responses in the range of 300–700 nm. This indicates that they all possess certain photoelectric conversion capability. The effects of component, structure, type of ligands of the complexes, valence state and coordination micro-environment of the central metal ions on the SPS were discussed. Furthermore, the SPS and UV–Vis absorption spectra were interrelated.     

Synthesis and characterization of a three-dimensional framework built up of paradodecatungstate-B clusters and transition metals as linkers

A novel paradodecatungstate compound, namely [Na₂(H₂O)₁₀][Cu₄(H₂O)₁₂(H₂W₁₂O₄₂)]·15H₂O (1) has been synthesized by convenient aqueous solution method and structurally characterized by single-crystal X-ray diffraction, IR spectra, elemental analysis, thermogravimetric analysis, and differential thermal analysis. Single-crystal X-ray diffraction reveals that in compound 1, the [H₂W₁₂O₄₂]^10? anions are connected via divalent copper cation as purely inorganic linker to form a three-dimensional structural network. In addition, compound 1 exhibits strong photoluminescent emission at room temperature.     

Two multi-dimensional frameworks constructed from zinc coordination polymers with pyridine carboxylic acids

Two novel zinc coordination polymers [Zn₂(H₂O)L(MoO₄)]_n (1) and [Zn₄(PO₄)₂L′(H₂O)]_n (2) (H₂L=2,2′-bipyridine-6.6′-dicarboxylic acid, H₂L′=2,2′-bipyridine-4,4′-dicarboxylic acid) have been hydrothermally synthesized and characterized by elemental analyses, IR spectra, UV spectra, single-crystal X-ray diffraction and thermogravimetric analyses. Structural analyses indicate that 1 represents a 2-D sheet structure built by dimeric [Zn₂L(H₂O)]²⁺ units and MoO₄^2– groups whereas 2 displays an interesting 3-D framework constructed by tetranuclear zinc clusters, L′^2? ligands and PO₄^3– groups. Examination of UV spectra suggests that both 1 and 2 can stably exist in the pH range of 2.45–5.45 and 3.01–8.55 in aqueous solution, respectively. The room-temperature solid-state photoluminescence of 1 and 2 are derived from the intra-ligands π–π? transitions of H₂L and H₂L′ ligands and the ligand-to-metal-charge-transfer transitions.     

Syntheses,structures and properties of four organic–inorganic hybrid nicotinate-bridging rare-earth-containing phosphotungstates

Four novel organic–inorganic hybrid nicotinate-bridging dimeric rare-earth (RE)-containing phosphotungstates [H₂N(CH₃)₂]₈[RE(H₂O)(NA)(α-HPW₁₁O₃₉)]₂·24H₂O (RE = Ho^III for 1, Er^III for 2, Tb^III for 3, Dy^III for 4; HNA = nicotinic acid) have been synthesized from the reaction of trivacant Keggin precursor Na₉[α-PW₉O₃₄]∙16H₂O, RE(NO₃)₃·6H₂O, HNA by employing dimethylamine hydrochloride as organic solubilizing agent in the conventional aqueous solution system, which have been further characterized by elemental analyses, IR spectra, thermogravimetric analyses and single-crystal X-ray diffraction. Structural analysis indicates that the hybrid dimeric {[RE(H₂O)(NA)(α-HPW₁₁O₃₉)]₂}⁸⁻ polyoxoanion in 1–4 can be considered as two head-to-head mono-RE-containing Keggin [RE(H₂O)(NA)(α-HPW₁₁O₃₉)]⁴⁻ subunits bridged by two (η²,μ-1,1)-nicotinate linkers, which stands for the first organic–inorganic hybrid RE-containing phosphotungstates functionalized by nicotinate ligands. What's more, the solid-state photoluminescence properties and lifetime decay behaviors of 1–4 have been measured at room temperature and their photoluminescence spectra display the characteristic emission bands of corresponding trivalent RE cations.     

Synthesis,spectral characterization,thermal, computational and antibacterial studies of lanthanide complexes with 2-fluorobenzoic acid-(5-R-2-hydroxy-benzylidene)hydrazide {R = chloro or bromo)

Tridentate Schiff base ligands, 2-Fluorobenzoic acid-(5-chloro-2-hydroxy benzylidene)hydrazide {H₂L_Cl} and 2-Fluorobenzoic acid-(5-bromo-2-hydroxybenzylidene)hydrazide {H₂L_Br} have been used to prepare a variety of lanthanide complexes [HNEt₃][LnL_x(NO₃)₂(H₂O)]H₂O, Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Er. The ¹H and ¹³C NMR of lanthanum in conjunction with the infrared, elemental, thermal, molecular mass and conductance measurements enable the assignment of the formula to these complexes. The anionic unit [LnL_x(NO₃)₂(H₂O)]^? contains one tridentate ONO-donor, L^2?, which coordinates the metal ions via the phenolate-O, the imine-N and the deprotonated amide-O atoms in enol tautomeric form. The coordination environment around central metal ion is completed by two bidentate nitrate ligands and one coordinated water molecule to give a coordination number of eight for Ln(III). In order to get a better insight into the structural features of the complexes, their molecular geometries were fully optimized using density functional theory calculations at the M06-2X/6-31G¹ level of theory. The antibacterial activity results, on a panel of six different bacterial strains, show that the activity of the complexes is higher than that of the free ligands and in some cases higher than that of amoxicillin which is taken as standard reference drug. Compared to the free ligands, the emission spectra of the complexes exhibit a blue-shift with a clear enhancement in the emission intensity.     

Kinetic study and UV–Vis spectra of 1:2 complexation of free base para‐substituted meso‐tetraphenylporphyrins with trimethylsilyl chloride

The UV–Vis spectra for 1:2 complexation of four different para‐substituted meso‐tetraphenylporphyrin (H₂t(4‐X)pp) and meso‐tetraphenylporphyrins (H₂tpp) with trimethylsilyl chloride (TMSC) displayed large and different redshifts (28–32.4 nm) of Soret and (15–41.7 nm) Q_(0‐0) bands, whereas 1:2 complexation of the less flexible tetramesitylporphyrin (H₂tmp) with TMSC led to rather small redshift (24.8 nm) of the Soret band and blueshift (−7.4 nm) of the Q_(0‐0) band. The varying spectral behavior for the porphyrins complexation seems to essentially reflect the different extent of π‐interactions between the meso‐aryl groups and the presumably saddled porphyrin macrocycle, through their relative coplanarity. The observed order of the rate constants for the complexation of various para‐substituted porphyrins, H₂t(4‐OCH₃)pp (9.27 ± 0.03) × 10⁻³ > H₂t(4‐CH₃)pp (6.68 ± 0.05) × 10⁻³ > H₂tpp (3.2 ± 0.05) × 10⁻³ > H₂t(4‐Cl)pp (8.36 ± 0.06) × 10⁻⁴, clearly demonstrated a higher reaction rate for the porphyrins containing para‐substituents with stronger electron donor ability. The calculated order for porphyrins (0.9 ± 0.1) and for TMSC (1.0 ± 0.1) suggests rate = K[Por][TMSC] for the complexation. Attempts were made to explain the absence of spectral evidence for the presence of an intermediate 1:1 (TMSC) Por adduct in terms of its high reactivity and/or relative instability. © 2007 Wiley Periodicals, Inc. 39: 231–235, 2007     

Spectral properties and solution behavior of gold(III) coordination compounds with water-soluble porphyrins

Gold(III) coordination compounds with three water-soluble porphyrins―5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (H₂TSPP^4–), 5,10,15,20-tetrakis(4-N-methylpyridyl)porphyrin (H₂TMPyP⁴⁺), and 5,10,15,20-tetrakis(4-N,N,N-trimethylaminophenyl)porphyrin (H₂TTMAPP⁴⁺)―have been studied. Complex [Au(TTMAPP)]⁵⁺ has been prepared for the first time. The analysis of coordination-induced shifts of proton signals in NMR spectra and intensities of Q bands in absorption spectra indicates the high degree of bond covalence in the studied metal porphyrins and a partial transfer of electron density from porphyrin to gold ion. The cationic complexes [Au(TMPyP)]⁵⁺ and [Au(TTMAPP)]⁵⁺ in aqueous solutions has been found to exist in monomeric form, while anionic complex [Au(TSPP)]^3– undergoes dimerization upon growth of concentration and solution ionic strength. Equilibrium constant for dimerization has been calculated, the constant has been found to decrease when temperature rises. Thermodynamic parameters of dimerization process have been determined: ΔH° =–31.8 kJ/mol and ΔS° =–13.8 J/mol K.     

Hydrogen chemical ionization mass spectrometry of metalloporphyrins

The hydrogen chemical ionization (H₂ CI) mass spectra of a range of metal(II) (Ni, Cu, Co, Pt), metal (III) (Al, Mn, Ga, Fe (bearing a single axial ligand)) and metal(IV) (Si, Ge, Sn (bearing two axial ligands) and V (as V?O²⁺)) porphyrins have been determined, The spectra are highly dependent on the coordinated metal, rather than the axial ligand(s) (where present). Ni(II), Cu(II), Mn(II or III), Ga(III), Ge(IV), Fe(III) and Sn(IV) porphyrins fragment via hydrogenation and demetallation, followed by cleavage of the resulting porphyrinogens at the meso(bridge) positions to give mono- and di-pyrrolic fragments. Tripyrrolic fragments are also observed in the case of Ni(II), Cu(II) and Sn(IV). Fragmentations of this type are similar to those observed for free-base porphyrins. In the case of Pt(II), Co(II), Al(III), Si(IV) and V(IV) (as vanadyl), the dipyrrolic fragment ions are either very weak or completely absent; hence their H₂CI spectra contain limited structural information. This variable CI behaviour may be related to the relative stabilities of the metalloporphyrins together with the multiple stable valency states exhibited by several metals.     

Two conformers in the solid state for a novel organotin(IV) complex of a phosphoramidate: Syntheses, spectroscopic study and crystal structures of several new organotin(IV) complexes of N-benzoylphosphoric triamides

Several novel organotin(IV) complexes with formula SnCl₂(CH₃)₂(X)₂, X = C₆H₅C(O)NHP(O)(NC₄H₈)₂ (1), C₆H₅C(O)NHP(O)(NC₅H₁₀)₂ (2), C₆H₅C(O)NHP(O)[N(CH₃)(C₆H₁₁)]₂ (3), C₆H₅C(O)NHP(O)[NH-C(CH₃)₃]₂ (4) were synthesized and characterized by ¹H, ¹³C, ³¹P NMR, IR spectroscopy and elemental analysis. The structures have been determined for each of the four compounds. Compound 1 exists in the form of two symmetrically independent molecules in the crystalline state due to differences in their similar torsion angles. In all of the four structures there are intramolecular -Sn-Cl?H-N- hydrogen bonds, in addition to weak C-H?O and C-H?Cl hydrogen bonds. Both ¹H and ¹³C NMR spectra show the coupling of ^119/117Sn nuclei with methyl proton and carbon atoms. The δ(³¹P) of these complexes are in upfields with respect to their corresponding reported ligands. The spectroscopic and structural properties of these complexes were compared with those corresponding ligands.     

CuSO4/sodium ascorbate catalysed synthesis of benzosuberone and 1,2,3-triazole conjugates: Design,synthesis and in vitro anti-proliferative activity

A novel series of conjugates of benzosuberone and 1,2,3-triazole i.e. 3-(4-phenyl-1H-1,2,3-triazol-1-yl)propyl-9-chloro-2,3-dimethyl-6,7-dihydro-5H-benzo[7]annulene-8-carboxylic acids (8a-j) were synthesized in good to excellent yields catalysed by CuSO₄ under milder reaction conditions and evaluated for their anti-proliferative activity. The structural elucidation of the prepared compounds was carried out using IR, ¹H NMR, ¹³C NMR and Mass spectral analysis. The newly synthesized derivatives (8a-j) were evaluated for their anti-proliferative activity against four human cell lines and the novel derivatives showed moderate to excellent activity. The obtained results suggest that these compounds can be considered as new hits for anti-proliferative drug development programme and further SAR studies can help obtain better anticancer agents.     

Modulation of fluorescence emission of 1-(2-pyridyl) pyrazole derived Schiff base ligands by exploiting their metal ion sensitive binding modes

Dioxomolybdenum(VI) complexes [MoO₂(B¹)H₂O] (1), [MoO₂(B²)EtOH] (2), [MoO₂(B³)EtOH] (3) and [MoO₂(B⁴)EtOH] (4) were synthesized using the Schiff base ligands H₂B¹(previously reported), H₂B², H₂B³ and H₂B⁴, respectively. These ligands were prepared by condensation of 1-(2-pyridyl) 5-methyl 3-pyrazole carbohydrazide with salicylaldehyde, o-hydroxy acetophenone, 5-bromo salicylaldehyde and 5-nitro salicylaldehyde respectively. Due to the presence of a substituted 1-(2-pyridyl) pyrazole unit, ligands H₂B¹, H₂B² and H₂B³ exhibit fluorescent emissions, and the most intense emission was obtained for H₂B³. H₂B⁴ is incapable of showing fluorescence emission. As the ligands are capable of using different binding modes, according to the demands of the guest metal ions, their emission properties also change accordingly. The dioxomolybdenum(VI) complex of the ligand H₂B¹, i.e. complex 1, shows quenched emission compared to H₂B¹. Again when Cu²⁺, Co²⁺ or Ni²⁺ ions are added to a solution of 1, in each case a new complex of Cu²⁺ Co²⁺ or Ni²⁺ is formed in solution and further quenching was observed. However, with Zn²⁺ input to a solution of 1, fluorescence recovery was observed up to the level of the free ligand. The copper(II) complex of H₂B¹ (complex 5), produced by adding equivalent amount of Cu²⁺ salt to a solution of 1, was isolated and characterized. One of the dioxomolybdenum(VI) complexes, 3, when subjected to an oxo-transfer reaction with PPh₃ produces complex [MoO(B³)CH₃CN] (6). Complex 6 shows reduced fluorescence emissions compared to 3 in the solid phase. These observations open up the possibilities for these ligands to work as fluorescent signaling system with different metal ion inputs. All the complexes are characterized by elemental analyses, electronic spectra, IR, ¹H NMR, magnetic measurements, EPR and by cyclic voltammetry. Complexes 1 and 5, as well as the ligands H₂B² and H₂B³, have been crystallographically characterized.     

Aufkl?rung der 1H- und 13C-NMR-spektren sowie der kristallstruktur unges?ttigter glycosylphosphonate und konformationsberechnungen an modellen1

By application of a modified LAOCN-3 program a complete elucidation of the ¹H NMR spectra of 2,3-unsaturated glycosyl phosphonates 1–5 could be achieved. The exactly determined ⁿJ(H, H) and novel ⁿJ(C, P) coupling constants are discussed, and permit a conclusive deduction of the conformations. The ¹³C NMR spectra of 1 to 6 can be fully interpreted. By a close inspection of chemical shifts as well as ¹J(C-H) and ⁿJ(C, P) coupling constants the conformational assignment is supported. For all the derivatives the correlations ¹J(C-1,H_e)>¹J(C-1, H_a) and ¹J(C-1, P_e) >¹J(C-1, P_a) can be used for the assignment of anomers. The crystal structure of 1 is in accordance with this assignment of anomers and displays an unexpected conformation. Calculations by MINDO-3 in resembling model compounds serve to elucidate such conformative effects.     

Spectroscopic and structural studies of chromate ions in zinc complexes with 2,2′-bipyridine. Analysis of the lowest triplet states in the CrO42− entity

Two novel complexes of Zn(II) chromate with 2,2′-bipyridine have been synthesised: [Zn(bpy)₃]CrO₄·7.5H₂O (1) and catena-(μ-CrO₄-O,O′)[Zn(bpy)(H₂O)₂]·2H₂O (2). Complex 1 has been characterised by a structural method. The [Zn(bpy)₃]CrO₄·7.5H₂O crystals have a monoclinic symmetry with space group C2/c and eight chemical units. The chromate ion is not coordinated to the zinc(II) ion. The O(3) and O(4) atoms of CrO₄²⁻ and O(8) of the water molecule statistically occupy their position with k=0.5, which means that the chromate ions execute reorientational motion between two equilibrium arrangements with equal probability. 4 K electronic spectra (1) revealed the vibrational fine structure in ν₃(F₂)=820 cm⁻¹ for the spin-forbidden ¹A₁→³T₁ transition. The pure electronic 0–0 transition in ¹A₁→¹T₁ was found at 20 270 cm⁻¹. In complex 2 the broad low intensity band at ca. 16 800 cm⁻¹ has been assigned to a forbidden ZnOCr transition in the bridge.     

Syntheses, crystal structure and electrochemical characterization of ferrocene-containing nickel(II) complexes with 4,11-dihydro-5,7,12,14-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine

In the title complexes, {[(η-C₅H₅)Fe(η-C₅H₄)(CO)](C₂₂H₂₁N₄)Ni} (1) and {[(η-C₅H₅)Fe(η-C₅H₄)(CO)]₂(C₂₂H₂₀N₄)Ni} (2), one and two electroactive ferrocenes (Fc) were grafted onto the methine of the nickel complex Nitmtaa (H₂tmtaa = 4,11-dihydro-5,7,12,14-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine) through the carbonyl groups. The two new complexes were characterized by IR, UV, MS and NMR spectra as well as by DSC measurements. The crystal structure of 1 was determined. Ni coordinates to four nitrogen atoms of tmtaa, and it is almost in the same plane as the N₄ plane. The mean Ni–N bond distance in the N₄ plane is 1.866 Å. The non-planar, saddle-shaped conformation of H₂tmtaa is almost retained in the nickel complex. The symmetry axis of ferrocene is almost parallel to the N₄ plane in Nitmtaa. The dihedral angle between the N₄ plane in Nitmtaa and the cyclopentadienyl ring in ferrocene is 98.5°. The electrochemistry of 1 and 2 was studied by cyclic voltammetry in CH₂Cl₂/1 × 10⁻¹ M n-Bu₄NClO₄ using a glass carbon working electrode. Because of the electron transfer between the electroactive ferrocene and the completely conjugated system of Nitmtaa, the complexes show novel electrochemical properties and the ferrocenes in 1 and 2 act as electron acceptors.     

Stepwise synthesis of two inorganic–organic hybrids based on the manganese monosubstituted Keggin polyanion chains

Two new hybrid compounds based on the manganese monosubstituted Keggin polyanion chains, [H₂bpy][Ag(bpy)]₂[HPMnMo₁₁O₃₉] (1) and [H₂bpy]₂[Hbpy][PMnMo₁₁O₃₉]·H₂O (2), (bpy = 4,4′-bipyridine) have been stepwise synthesized under hydrothermal condition and characterized by elemental analyses, IR spectra, thermogravimetry, and single-crystal X-ray diffraction technique. Structural characterization reveals that although both 1 and 2 contain manganese monosubstituted Keggin polyanion chains, the polyanion chains are not in the full consistent way. In 1, the neighboring manganese monosubstituted Keggin clusters are connected via sharing the para position oxygen atoms of the clusters to form a linear polyanion chain in which the monosubstituted Keggin clusters are further grafted by silver coordination polymer chains forming a 2D network. Whereas the polyanion chain in 2 exhibits a zigzag structure, which is formed by sharing the metaposition terminal oxygen atoms of the clusters, rather than para position terminal oxygen atoms as that in 1. Each zigzag chain contacts with four adjacent chains along four directions through short interspecies contacts, forming a 3D supramolecular framework. The protonated Hbipy⁺ and H₂bipy²⁺ molecules as the counter cations exist in voids of the supramolecular framework in 2. Furthermore, photocatalytic experiments indicate that 1 has good activities for photocatalytic degradation of RhB under UV irradiation.     

Novel mixed-ligand complexes of coumarilate/<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-diethylnicotinamide with some transition metals

Coordination complexes of transition metal cations (Co^II, Ni^II, Cu^II and Zn^II) containing coumarilate and N,N′-diethylnicotinamide were synthesized. The structural characterization and thermal behaviour analysis of novel samples synthesized were conducted through elemental analysis, magnetic susceptibility, solid-state UV–Vis, direct and injection probe mass spectra, FTIR spectra, thermoanalytic TG-DTG/DTA and single crystal X-ray diffraction methods. The structural details of single crystals of [Co(dena)₂(H₂O)₄](coum)₂ (I) and [Cu(coum)₂(dena)₂(H₂O)₂] (III) complexes were resolved completely. Moreover, the results of analysis obtained for [Ni(coum)₂(dena)₂(H₂O)₂] (II) and [Zn(dena)₂(H₂O)₄](coum)₂ (IV) complexes were interpreted considering the samples with crystal structures defined and made assumptions about the structural details. It was determined that the complex of Co^II metal cation has salt-type structure and the coordination number of metal is accomplished to six as the sum of 4 mol of water and also 2 mol of N,N′-diethylnicotinamide ligands in trans position located within the coordination sphere. It was observed that 2 mol of coumarilate anions are located outside the coordination sphere and have stabilized to the charge (2+) of metal. The Cu^II complex has totally molecular structure, and the coordination sphere of metal cation was 6 as the sum of 2 mol of water, 2 mol of N,N′-diethylnicotinamide and 2 mol of monoanionic monodentate coumarilate ligands. All ligands have been located in –trans position. The geometry of both complex structures is distorted octahedral. It is assumed that the Ni^II complex structure is isostructural with Cu^II complex structure and also does Zn^II complex with Co^II structure. It was determined that the decomposition products obtained from thermal analysis are the oxides of related metal cations.     

Synthesis,Characterization, Redox Properties,and Photodynamics of Donor–Acceptor Nanohybrids Composed of Size‐Controlled Cup‐Shaped Nanocarbons and Porphyrins

Cup‐shaped nanocarbons (CNC) generated by the electron‐transfer reduction of cup‐stacked carbon nanotubes have been functionalized with porphyrins (H₂P) as light‐capturing chromophores. The resulting donor–acceptor nanohybrid has been characterized by thermogravimetric analysis (TGA), Raman and IR spectroscopy, transmission electron microscopy, elemental analysis, and UV/Vis spectroscopy. The weight of the porphyrins attached to the cup‐shaped nanocarbons was determined as 20 % by TGA and elemental analysis. The UV/Vis absorption spectrum of CNC? (H₂P)_n in DMF agrees well with that obtained by the superposition of reference porphyrin (ref‐H₂P) and cup‐shaped nanocarbons. The photoexcitation of the CNC? (H₂P)_n nanohybrid results in formation of the charge‐separated (CS) state to attain the longest CS lifetime (0.64±0.01 ms) ever reported for donor–acceptor nanohybrids, which may arise from efficient electron migration following the charge separation. The formation of a radical ion pair was detected directly by electron spin resonance (ESR) measurements under photoirradiation of CNC? (H₂P)_n with a high‐pressure mercury lamp in frozen DMF at 153 K. The observed ESR signal at g=2.0044 agrees with that of ref‐H₂P^.+ produced by one‐electron oxidation with [Ru(bpy)₃]³⁺ in deaerated CHCl₃, indicating the formation of H₂P^.+. The electron‐acceptor ability of the reference CNC compound (ref‐CNC) was also examined by the electron‐transfer reduction of ref‐CNC by a series of semiquinone radical anions.     

A thermochemical study of dissociative ionization of 4,4-dimethyl-1-thia-4-silacyclohexane and 2,3,3-trimethyl-1-thia-3-silacyclopentane. Decomposition pathways to produce a dimethylsilanethione ion-radical [Me2SiS]+•

The dissociative ionization of 4,4-dimethyl-1-thia-4-silacyclohexane (I) and 2,3,3-trimethyl-1-thia-3-silacyclopentane(II) has been studied by electron photoionization (PI) mass spectrometric methods. The molecular ion fragmentation is mainly related to the loss of ethylene and results in a [Me₂SiSC₂H₄]^+? (m/z 118) ion-radical (A). Further loss of ethylene from A produces a dimethylsilanethione [Me₂SiS]^+? (m/z 90) ion-radical (B). The latter is the most abundant ion in the mass spectra of I and II at 70 eV.The ionization energies (IE) of I (8.22 ± 0.07 eV) and II (8.06 ± 0.03 eV) and the appearance energies (AE) of ion-radicals A and B have been determined. Also, the following heats of formation were calculated (kJ/mol): ΔH_f⁰(I) = ?31.1; ΔH_f⁰(II) = ?65.8; ΔH_f⁰(M_I^+?) = 762.0; ΔH_f⁰(M_II^+?)= 712.1; ΔH_f⁰(A)_aver = 780.2; ΔH_f⁰(B)_aver = 847.7.     

Synthesis and characterization of meso-ferrocenylethynyl 5,15-diphenylporphyrins

A series of four meso-ferrocenylethynyl (5,15-diphenylporphyrinato)nickel(II) derivatives have been synthesized by Sonogashira coupling reactions. Three of these compounds contain the electron-withdrawing groups including -CHO, -CHC(CN)₂, and -CCC₆H₄NO₂ at the remaining meso position, with a view to preparing push-pull chromophores, in which ferrocene serves as the electron donor. All the new compounds have been characterized spectroscopically and the molecular structure of one of these porphyrins (compound 11) has also been determined. The studies show that although the ferrocenylethynyl group can extend the π system of the central porphyrin core, the cyclopentadienyl rings of ferrocene are almost orthogonal to the porphyrin ring. This hinders ferrocene serving as a good electron donor in these systems.