Protonation of Pyridyl‐Substituted TTF Derivatives: Substituent Effects in Solution and in the Proton–Electron Correlated Charge‐Transfer Complexes

Protonated pyridyl‐substituted tetrathiafulvalene electron‐donor molecules (PyH⁺‐TTF) showed significant changes in the electron‐donating ability and HOMO–LUMO energy gap compared to the neutral analogues and gave a unique N⁺?H???N hydrogen‐bonded (H‐bonded) dimer unit in the proton–electron correlated charge‐transfer (CT) complex crystals. We have evaluated these features from the viewpoint of the molecular structure of the PyH⁺‐TTF derivatives, that is, the substitution position of the Py group and/or the presence or absence of the ethylenedithio (EDT) group. Among 2‐PyH⁺‐TTF ( 1 o H⁺ ), 3‐PyH⁺‐TTF ( 1 m H⁺ ), 4‐PyH⁺‐TTF ( 1 p H⁺ ), and 4‐PyH⁺‐EDT‐TTF ( 2 p H⁺ ) systems, the para‐pyridyl‐substituted donors 1 p H⁺ and 2 p H⁺ exhibit more marked changes upon protonation in solution; a larger redshift in the intramolecular CT absorption band and a larger decrease in the electron‐donating ability. Furthermore, the EDT system 2 p H⁺ has the smallest intramolecular Coulombic repulsion energy. These differences are reasonably interpreted by considering the energy levels and distributions of the HOMO and LUMO obtained by quantum chemical calculations. Such substituent effects related to protonation were also examined by comparing the structure and properties of a new H‐bonded CT complex crystal based on 2 p H⁺ with those of its 1 p H⁺ analogue recently prepared by us: Both of them form a similar type of H‐bonded dimer unit, however, its charge distribution as well as the overall molecular arrangement, electronic structure, and conductivity were significantly modulated by the introduction of the EDT group. These results provide a new insight into the structural and electronic features of the PyH⁺‐TTF‐based proton–electron correlated molecular conductors.     

Analysis of optical absorption spectra of transition metal cluster ions by the spin-polarized DV-Xα method

Optical absorption spectra of cobalt cluster ions, Co _n ⁺ , and vanadium cluster ions, V _n ⁺ , were analyzed by a theoretical calculation based on the spin-polarized DV-Xα method, and their electronic and geometric structures were obtained. Relative absorption cross section associated with each electronic transition was calculated; the calculation enables a qualitative comparison of calculated spectrum with a measured one not only in its transition energy but also in its intensity profile. This analysis shows that Co ₄ ⁺ , Co ₃ ⁺ , and V ₄ ⁺ have, respectively, a tetrahedral structure with a bond distance of 2.00Å, an equilateral triangle with a bond distance of 2.30Å, and a distorted tetrahedral structure with five bonds having a distance of 2.34 Å and one of 2.89Å. The differences in the population between majority and minority spins (spin-difference) evaluated from the electronic structure thus obtained were 2.0, 1.7, and zero per atom in Co ₃ ⁺ , Co ₄ ⁺ , and V ₄ ⁺ , respectively. These spin differences indicate a ferromagnetic and an antiferromagnetic spin-coupling in the cobalt and vanadium cluster ions, respectively.     

Darstellung und Charakterisierung von Phthalocyanin-π-Kation-Radikalen von H+, Mg2+ und Cu2+

Preparation und Characterization of Phthalocyanine-π-Cation-Radicals of H⁺, Mg²⁺, and Cu²⁺ The preparation of phthalocyanine-π-cation-radicals (Pc(?1)) of H⁺, Mg²⁺, Cu²⁺ is described. MgClPc(?1) and Cu(NO₃)Pc(?1) · HNO₃ are isolated as stoichiometrically pure, stable redbrown solids. Contrary to the phthalocyanines(?2) (Pc(?2)) these are very soluble with redviolet colour in organic solvents in the presence of R? COOH (R ? H, CF₃, CCl₃). The electronic absorption absorption spectra (UV-VIS) are remarkably solvent-dependent. This solvent effect is due to a reversible radical association. Monomeric radical species exist in nonpolar (CH₂Cl₂), dimeric in polar solvents (CH₃NO₂, C₂H₅OH). The UV-VIS, infrared (IR), and resonance-raman (RR) spectra of MgClPc(?1) and Cu(NO₃)Pc(?1) · HNO₃ are discussed and compared with the analogoues spectra of MgPc(?2) · 2 H₂O and MgPc(?2) · HCl. Although there are only minor differences in the chemical composition and the electronic structure the spectroscopic data vary significantly for every complex. Especially the IR spectrum is suitable for a quick demonstration of the π-cation-radicals. The diagnostic bands are at ca. 1350 and 1450 cm^?1.     

Studies of C. I. Acid Red 186 and Metal Complexes with Uo++2, Ce3+ and Th6+ Ions

The electronic absorption spectra of C. I. Acid Red 186 are studied in solution of different pH. The pK values of the acid-base equilibria set are determined and commented upon. The complexes of UO⁺⁺₂, Ce³⁺ and Th⁴⁺ ions are investigated by some spectroscopic techniques and potentiometric titration. The formation of 1:1, 1:2 and 1:2 complexes (M:L) with UO₂⁺⁺, Ce³⁺ and Th⁴⁺ respectively is confirmed and their conditional stability constants are determined. The solid complexes are prepared and analysed for their metal content, their ir spectra are disussed in comparison to that of the ligand to establish the bonding between the ligand and metal ions.     

The mass spectra of alkyl phenyl tellurides

The mass spectra of several alkyl phenyl tellurides, C₆H₅TeR (R = CH₃, CD₃, C₂H₅, n-C₃H₇, i-C₃H₇ and n-C₄H₉) have been studied with special emphasis on the fragmentation patterns involving cleavage of the alkyl and aryl tellurium–carbon bonds. Each compound exhibited intense parent ions. The rearrangement ions [C₆H₆Te]⁺? and [C₆H₆]⁺? were found in the spectra of phenyl ethyl and higher tellurides. Two other rearrangement ions [HTe]⁺ and [C₇H₇]⁺ were observed in the spectrum of each compound. Examination of the mass spectrum of phenyl methyl-d₃ telluride demonstrated that the [HTe]⁺ ions derive hydrogen from the phenyl group.     

Kinetic-energy spectroscopy of high-rydberg fragments from keV collisions of H2+, D2+, N2+ and C2+ ions with rare-gas atoms

A method for measuring the kinetic-energy spectrum of high-Rydberg fragments from collisions of keV molecular ions with rare-gas atoms is described. The kinetic-energy spectra of high-Rydberg fragments from the collisions between D₂⁺, H₂⁺, N₂⁺ and C₂⁺ ions having 8 keV kinetic energy and thermal He and Xe are reported. Two single-collision processes for the generation of high-Rydberg fragments have been identified.     

Extension of High‐Resolution Optical Absorption Spectroscopy to Divalent Neodymium: Absorption Spectra of Nd2+ Ions in a SrCl2 Host

There is a lack of information on electronic spectra of divalent neodymium, and thus the synthesis and characterization of Nd²⁺ systems is now reported. Stabilization of neodymium is observed in a chloride host, which importantly has been accomplished with Nd ions introduced in a divalent state during synthesis, unlike by γ‐irradiation of Nd³⁺ system employed previously. This method yields good‐quality SrCl₂:Nd²⁺ single crystals. For the first time the electronic absorption spectra of Nd²⁺ doped in SrCl₂ have been recorded with high resolution at liquid helium temperature (4.2 K). Identification of the absorption bands occurring in the spectral range of 5000–40 000 cm⁻¹ (2000–250 nm) has been achieved and their tentative assignment proposed. This uniquely detailed Nd²⁺ absorption spectrum provides basis for fingerprinting method enabling identification of the presence of Nd²⁺ ions in future spectra as well as in existing but as‐yet not fully resolved spectra.     

Mass Spectra of New Heterocycles. XVII. Main Fragmentation Routes of Molecular Ions of 4-Alkoxy-5-amino-3-methylthiophene-2-carbonitriles under Electron and Chemical Ionization

For the first time decomposition was investigated of 4-alkoxy-5-amino-3-methylthiophene-2-carbonitriles under the conditions of electronic (70 eV) and chemical (reagent gas methane) ionization. At the electronic ionization the compounds under study [except for 4-(1-ethoxyethoxy) and 4-(ferrocenylmethoxy) derivatives] form stable molecular ions that decompose mainly by the cleavage of an alkyl radical from the alkoxy-substituent. Further fragmentation of the arising ion [M–Alk]⁺ depends on the substituent nature in the amino group. In the mass spectrum of 4-(ferrocenylmethoxy)-substituted thiophene peaks of the ion [FcCH₂]⁺ and its fragmentation products prevail. In the mass spectra of chemical ionization predominant peaks belong to ions M^+·, [M + H]⁺ and [M + C₂H₅]⁺, and fragment ions are absent.     

Metal Ion Interaction of Two New Tritopic N2O13 Macrobicycles with B15C5 Moieties in Acetonitrile Solution

The synthesis of two new tritopic crown ligands (L1 and L2) bearing two benzo-15-crown-5 lateral moieties linked through a dibenzo-trioxa chain together with their interaction with metal ions, in acetonitrile and acetonitrile–water (50%, v/v) solutions is reported. The influence of K⁺, Na⁺, Li⁺, Ca²⁺, Ba²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺ and Al³⁺, on the spectroscopic properties of these diaza-polyoxa ligands was investigated by absorption spectrophotometry and in some cases by fluorescence emission spectroscopy. Coordination with alkaline (Na⁺, K⁺ and Li⁺) and alkaline earth (Ca²⁺and Ba²⁺) metal ions is assumed to be weak with both macrobicyclic ligands, while the interaction with both imine and amine derivatives causes a minor effect in the absorption spectra. Coordination with Cu²⁺, Zn²⁺ and Pb²⁺ in acetonitrile solution causes a major change in the absorption spectra of the chromophores. In the case of Cu²⁺, addition of the metal to L1 or L2 leads to a blue–violet complex in solution with an absorbance maximum centred at 590 nm. Interaction of the Schiff-base L1 with Pb²⁺ leads to a short wavelength shift in the absorption bands, comparable with the ZnL1 complex. Presence of transition metal ions such as Co²⁺, Ni²⁺and Cd²⁺ do not remarkably affect the absorption spectra of L1 and L2 in solution. Trivalent aluminium has a modest effect in the absorption bands of both N₂O₁₃ donor set bismacrocyclic ligands. The fluorescence study of L2 in the presence of Na⁺, K⁺, Ca²⁺, Ba²⁺, Co²⁺, Cu²⁺, Ni²⁺, Pb²⁺ and Al³⁺shows that Cu²⁺, Pb²⁺ and Al³⁺ complexes form non-fluorescent complexes.     

The colours of simple salts of the violurate anion

Salts of the violurate anion with the alkali and alkaline earth metals, the d¹⁰ ions Zn²⁺ and Cd²⁺, Mn²⁺, Pb²⁺, Ag⁺ and the lanthanides show a variety of spectacular colours in the solid state. The metal ions have no intrinsic absorption in the visible region (apart from the weak spin-forbidden bands of Mn²⁺) and do not normally show charge-transfer absorption. The colours are ascribed to the n→π* transition of the violurate anion. As confirmation of this assignment the visible absorption of the K⁺ salt is shown to be polarized perpendicular to the plane of the violurate anion. Low temperature (∼20 K) absorption spectra of the Na⁺, K⁺ and Rb⁺ salts are reported.     

Fast atom bombardment mass spectra of telluronium salts

The fast atom bombardment (FAB) mass spectra of telluronium salts were studied. The spectra exhibit the intact cation (C⁺) and cluster ions ([M + C]⁺). The principal fragment ions in the FAB mass spectra of telluronium salts are [RTe]⁺, [R₂Te]⁺˙, [R₂Te − H]⁺, [RTeR′]⁺˙, and [RTeR′ + H]⁺. When the anion was [BPh₄]⁻, interesting cluster ions such as [M + C − BPh₃]⁺ appeared.     

On [Na(POCl3)4]+ Complex Ion Formation: Conductivity,Raman, and NMR studies in the system phosphoryl chloride–sodium tetrachloro aluminate and related compounds

The system POCl₃–NaAlCl₄ was investigated by measuring the conductivity and the Raman and NMR spectra (²⁷Al, ²³Na and ³¹P) as a function of the mol fraction x of NaAlCl₄ in POCl₃. Additionally, Raman spectra of POCl₃ solutions of NaFeCl₄, LiAlCl₄, LiFeCl₄, and KAlCl₄ were recorded. In solutions containing Li⁺ or Na⁺ ions a liquid to solid (or jelly) phase transition was observed under certain conditions, dependent on salt concentration and temperature. Observed changes in the Raman spectra of the electrolyte solutions in comparison to the pure solvent POCl₃ demonstrate the existence of interactions. Clearly, the POCl₃ eigenfrequencies and hence the molecules are pertubed. The formation of [M(POCl₃)₄]⁺ complexes (M = Li, Na) can be deduced from the Raman measurements. NMR investigations support this conclusion. For assigning of Raman spectra, (Li⁺, K⁺) cation and ([FeCl₄]^?, [SbCl₆]^?) anion substitutions were employed.     

Optical and ESR studies of silver clusters

The optical and ESR spectra of Ag(O), Ag₂⁺ and Ag₄³⁺ centres formed in γ-irradiated aqueous and ethanol glasses have been monitored under identical conditions. The ESR spectra of the Ag(O) centres sugest that they initially retain the solvation of the parent Ag⁺ ions but that solvent molecules are gradually lost on annealing. This loss is reflected in marked high-frequency shifts in the electronic transitions. An intense band observed in the range 265–290 nm grew in simultaneously. This is assigned to Ag₂³⁺ ions. These have a well characterised ESR spectrum, but have not previously been studied optically.     

Preparation and characterization of tetra(4-pyridyl)porphyrinatomanganese(III) cation supported covalently on poly(siloxane)

Tetra(4-pyridyl)porphyrinatomanganese(III), [Mn^III(TPyP)]⁺, has been covalently bonded to the surface of a chlorinated crosslinked poly(siloxane) which contains the immobilized chloropropyl group, -CH₂CH₂CH₂Cl. The metalloporphyrin complex was found to react with the immobilized ligand via a quaternization reaction of the 4-pyridine N-atom. The porphyrin binding involves a chemical process rather than physical adsorption. There is evidence that two porphyrins species coexist, both bonded to the surface, one being [Mn^III(TPyP)]⁺ and the other (H₂TPyP), both in the quaternary salt forms, when the quaternization reaction is carried out at higher temperature (150 °C). At moderate reaction temperatures (70–80 °C) the quaternization reaction resulted in only one species, supported [Mn^III(TPyP)]⁺, as evident from electronic spectra of the solid. Also, visible absorption spectra taken of the solution remaining after the quaternization reaction showed no demetallated porphyrm. Solid state electronic absorption, dispersive IR and FT-IR spectra have been used for confirmation.     

Linear and Star-Shaped Extended Di- and Tristyrylbenzenes: Synthesis,Characterization and Optical Response to Acid and Metal Ions

Two linear 1,4-distyrylbenzenes and five star-shaped 1,3,5-tristyrylbenzene derivatives ( L_2a and L_2b , Y₀–Y₃ and Y_NBu ) were synthesized and spectroscopically characterized. The photophysical properties, optical response to acid and metal ions were investigated. Upon backbone extension of linear distyrylbenzenes or the introduction of dibutylanilines, the electronic spectra are redshifted. Incorporation of electron-deficient pyridyl units does not significantly affect the optical properties. Variation of the number of pyridine rings and substitution pattern tune the fluorescence response to acids and metal ions. The novel arenes discriminate Al³⁺, Mn²⁺, Fe³⁺, Fe²⁺, Cd²⁺, Ag⁺ and Hg²⁺.     

Nitrosolate und Nitrosolatokomplexe. III. Darstellung und Struktur von Nitrosolsäurederivaten organosubstituierter Antimon(V)-, Tellur(IV)- und Jod(III)-Verbindungen

Nitrosolates and Nitrosolatocompounds. III. Synthesis and Structures of Nitrosolate Derivatives of Organosubstituted Compounds of Antimony(V(, Tellurium(IV), and Iodine(III) In solution the derivatives of the nitrosolates of acetic and benzoic acids and of the ions (C₆H₅)₄Sb⁺, (CH₃),Sb⁺, (C₆H₅)₃Te⁺, and the derivative of the nitrosolate of acetic acid and of the ion C₁₂H₈I⁺ show ionic or covalent structures, depending on the polarity of the solvent. In the solid state only the derivatives of (C₁₂H₅)₄Sb⁺ unequivocally do not display salt character. The structure of (C₆H₅)₄Sb · O₂N₂C–CH₃ was determined by X-ray methods. The compound consists of separated molecules with slightly distorted trigonal-bipyramidonal environment of the antimony atom. The nitrosolato ligand is oxygen bonded to one of the apical positions. According to the electronic spectra of the solutions of the nitrosolate derivatives the nitrosolate ions react in the covalent forms either as uni-dentate ligands with O-coordination or as bidentate chelating or bridging ligands with O,O′-coordination.     

The elusive methene ylides CH2CIH,CH2FH and CH2OH2

The possible existence of the ylides CH₂CIH, CH₂₅FH and CH₂OH₂ as stable neutral species in the gas phase has been investigated by the neutralization–reionization (NR) mass spectrometry of their radical cations using a double-focusing mass spectrometer of reversed geometry. The experiments were, for the most part, performed under single-collision conditions with Xe as the neutralization target gas and He and O₂ as reionization agents. For each ylidion a peak was observed in their NR mass spectrum which indicated that the neutral ylide had apparently been produced. However for CH₂FH⁺˙ and CH₂OH₂⁺˙ the m/z 34 and m/z 32 peaks, respectively, were attribut-able to interferences from the natural isotopic abundance of ions of lower mass. For CH₂CIH⁺˙, the NR recovery signal was found to arise from the presence of CH₃CI⁺˙ as an impurity in the ylidion flux. This was proved by examination of the collisional activation mass spectra of the [C, H₃, CI]⁺˙ ions produced in the NR mass spectra of the conventional ions and ylidions, an experiment performed using a triple-sector mass spectrometer.     

Steric interaction of solvation and sterically enhanced halogeno complexation of manganese(II), cobalt(II) and nickel(II) ions inN,N-dimethylacetamide

The complexation of manganese(II), cobalt(II) and nikel(II) with bromide ions has been studied in N,N-dimethylacetamide(DMA) by calorimetry and spectrophotometry. The formation of [MBr]⁺, [MBr₂] and [MBr₃]^– (M=Mn, Co, Ni) was revealed in all the metal systems. Interestingly, the complexation is significantly enhanced in DMA over N,N-dimethylformamide (DMF). This is unusual because physicochemical properties of DMA and DMF as solvent are similar. Furthermore, extracted electronic spectra of individual complexes of Ni^II suggested the presence of a geometry equilibrium, [NiBr(DMA)₅]⁺=[NiBr(DMA)₄]⁺+ DMA, in DMA. A similar geometry equilibrium is also suggested, [NiBr₂(DMA)₃]=[NiBr₂(DMA)₂]+DMA. Such geometry equilibria were not observed in DMF. With regard to cobalt(II), electronic spectra show the presence of the four-coordinated [CoBr(DMA)₃]⁺ complex in DMA, unlike the six-coordinated [CoBr(DMF)₅]⁺ one in DMF. These facts suggest that a specific strong steric interaction operates between coordinating solvent molecules, which plays a key role in the complexation behavior of the divalent transition metal ions in DMA.     

Chemical ionization mass spectrometry of halomethanes with tetramethylsilane as reagent gas

Chemical ionization mass spectra of halomethanes measured using tetramethylsilane as reagent gas exhibit three major peaks corresponding to [M + SiMe₃]⁺, [M − X]⁺ and (MeSi)₂X⁺ ions (X = Cl, Br or I). Dihalomethanes CH₂X₂ form the most stable silylated molecular ions, whereas in the mass spectra of tetrahalomethanes (CX₄) these ions have not been detected and the ions CX₃⁺ are the most abundant. Production of bistrimethylsilyl-halonium ions is the most pronounced process for haloforms (CHX₃).     

Photodissociation spectrum of CH3I+ prepared by multiphoton ionization

Two-photon resonant multiphoton ionization has been used to prepare rotationally cooled and selected CH₃I⁺ ions with controlled vibrational and electronic distributions. These ions are photodissociated by a second laser. The highly simplified photodissociation spectrum displays a clear dissociation threshold as well as bands hidden in earlier spectra. The data suggests corrections to previously determined vibrational constants.