Steric conditions and polarizability of structurally symmetrical interamoleculer hydrogen bonds in R-DI(α-pyridyl) hydroperchlorates

Seven R-di-(α-pyridyl) hydroperchlorates (R = (1) CH₂, (2) NH, (3) CO, (4) (CH₂)₂, (5) (CH₂)₃, (6) (CH₂)₄ and (7) S-S) were prepared and studied in acetonitrile-d₃ solutions by NMR and IR spectroscopy. With the hydroperchlorates of compounds 1 and 4, an equilibrium between non-hydrogen-bonded NH⁺ groups and intramolecular-bonded NH⁺ groups is present. With compounds 2, 3 and 5–7, the intramolecular hydrogen bonds are formed quantitatively. In compounds 4–7, the potential wells in these intramolecular structurally symmetrical N⁺H· N ? N · H⁺N bonds, are double minima. These hydrogen bonds are easily polarizable. With compounds 1–3, the distance between the N atoms given by the steric conditions of the molecules is smaller than with usual linear hydrogen bonds. Therefore, strong bent intramolecular structurally symmetrical hydrogen bonds are found, with relatively narrow single-minimum potential wells. These bonds cause a band in the region 3000–2500 cm^?1 instead of the continuum. Thus they are not easily polarizable.     

Bildung siliciumorganischer Verbindungen. XXXIX. Teilchlorierte Carbosilane

1. Photochlorination in CCl₄ of the Si-chlorinated carbosilanes (Cl₃Si? CH₂)₂SiCl₂ and (Cl₂Si? CH₂)₃ leads to totally chlorinated compounds, e. g. (Cl₃Si? CCl₂)₂SiCl₂. After chlorination has started at one CH₂ group, formation of a CCl₂ group is preferred before another CH₂ group is involved into the reaction. Thus preparation of compounds a, b, c is possible. Cl₃Si? CCl₂? SiCl₂? CH₂? SiCl₃ (a) for (b) and (c) (see “Inhaltsübersicht”). SO₂Cl₂ (benzoyl peroxide) as chlorinating agent reacts more slowly, and opens an access to carbosilanes containing CHCl groups such as (d), Cl₃Si-CHCl? SiCl₂? CH₂? SiCl₃ (e). Reactions of compounds (a) to (d) with LiAlH₄ yields carbosilanes with SiH groups, and partially chlorinated C atoms. 2. By the high reactivity of Si? CCl₂? Si groups an exchange of Cl atoms of CCl groups in perchlorinated carbosilanes is possible for H atoms of Si? H groups in perhydrogenated carbosilanes, thus allowing the preparation of compounds containing CHCl and SiHCl groups, e. g. according to Gl.(1) (Inhaltsübersicht). Further reactions, formulated as the last equations in Inhaltsübersicht, are reported as well as the rearrangement of H₃Si? CHCl? SiH₃.     

Theoretical studies of the spectroscopic properties of blue emitting iridium complexes

Electronic structures, absorptions and emissions of a series of (ppy)₂Ir(acac) derivatives (ppy = 2- phenylpyridine; acac = acetoylacetonate) with fluoro substituent on ppy ligands were investigated theoretically. The ground and excited states geometries were fully optimized at B3LYP/LANL2DZ and CIS/LANL2DZ level, respectively. The HOMO is composed of d(Ir) and π(C^∧N), while the LUMO is localized on C^∧N ligand. The absorptions and emissions in CH₂Cl₂ media were calculated under the TD–DFT level with PCM model. The lowest-lying absorption of these complexes is dominantly attributed to metal-to-ligand and intraligand charge transfer (MLCT/ILCT) transitions and the emission of them originates from ³MLCT/³ILCT excited states. The absorption and emission of these complexes are blue-shifted by increasing the number of fluoro on phenyl, but the spectra are red-shifted by adding fluoro on pyridyl. While a single fluoro of different substituted site on phenyl results in different extent blue-shift to the spectra.     

Synthesis,fluorescence properties,and conformational analysis of ether-linked (1,8)pyrenophanes

Mono-, di- and oligo-ether linked (1,8)pyrenophanes 1–7 were synthesized, and their fluorescence and conformational properties in the absence and presence of metal ions were elucidated. Fluorescence spectra of 1.0 × 10⁻⁵ M solutions of the mono- and di-ether linked pyrenophanes 1–5 were comprised of only monomer emission bands, while those of the oligoethylene glycol linked analogs 6 and 7 contained both monomer and intramolecular excimer emission bands. Addition of perchlorate salts of Ba²⁺, Na⁺ and Li⁺ to 1:1 v/v CH₃CN:CH₂Cl₂ solutions of 6 and 7 caused decreases in the intensities of the corresponding intramolecular excimer emission bands and, in some cases, increases in the intensities of the monomer emission. Monomer and intramolecular excimer emission from the (1,8)pyrenophanes are suggested to arise from the respective anti and syn conformers, whose ratios are dependent on solvent polarity, temperature and kinds of added metal ions.     

A highly selective fluorescent sensor for fluoride anion based on pyrazole derivative: Naked eye “no–yes” detection

A new pyrazole-based fluorescent sensor, 5-amino-3-(5-phenyl-1H-pyrrol-2-yl)-1H-pyrazole-4-carboxamide (compound 1), was studied for fluoride anion (F^?) detection in organic or water-containing solution. This compound displayed both changes in UV–vis absorption and fluorescence emission spectra upon addition of F^?. With increasing of F^?, blue emission intensity increases drastically and reaches saturation with 607-fold enhancement at 424 nm. The results indicate that compound 1 has highly selectivity for fluoride detection over other anions, such as Cl^?, Br^?, I^?, HSO₄^?, H₂PO₄^? and AcO^? in DMSO or aqueous DMSO solutions. ¹H NMR titration and other experiments confirm that the sensing process is mainly from the deprotonation of the pyrazole–NH in compound 1.     

Reactions of photogenerated fluorine atoms with dopant molecules in solid argon

The products of UV photolysis of ternary Ar?CH₄(CD₄)?F₂ mixtures (1:c:c ₀,c, c ₀=0.001–0.01) at 13–16 K were identified by ESR and FTIR spectroscopy. These products are^?CH₃ (^?CD₃) radicals of typesI andII and molecular CH₃F?HF complexes. The latter were characterized by the IR bands of the stretching C?F (1003 cm^?1) and H?F (3774 cm^?1) vibrations. The ESR spectra of radicalsI are asymmetric. The anisotropy of theg-factor (Δg～10^?3) of radicalI indicates that the structure of the radicals is nonplanar. The ESR spectrum of the typeII radical is identical to that of matrix-isolated^?CH₃ (^?CD₃) radicals with the planar structure (Δg<5·10^?5). Under the experimental conditions, the amount of complexes formed in the photolysis is equal to 0.022·c. When the photolysis is ceased, radicalI disappears after ≈10³ s and radicalII is stabilized. The limiting concentrations of the stabilized^?CH₃ and^?CD₃ radicals are equal to 2·10^?2·c and 2·10^?3·c, respectively. A mechanism of the formation of the products is suggested. It is based on the assumption that both matrix-isolated CH₄ and F₂ and their heterodimers CH₄?F₂ are present in the samples and it takes into account the long-range migration of translationally excited flourine atoms. The CH₃F?HF complexes and radicalsI are generated by the photolysis of the CH₄?F₂ heterodimers. The decay of radicalsI is caused by geminate recombination of proximate F...CH₃ pairs. RadicalsII are formed in the reaction of translationally excited fluorine atoms with isolated CH₄ (CD₄) molecules.     

Thiazole-based chemosensor II: synthesis and fluorescence sensing of fluoride ions based on inhibition of ESIPT

Novel chemosensors based on 2-(2′-hydroxyphenyl)-4-phenylthiazole were synthesized and their anion sensing behaviors were investigated. Sensors 1 and 2 show fluoride ion selective behaviors related to their absorption and emission spectra amongst F^?, CH₃CO₂ ^?, H₂PO₄ ^?, Cl^?, Br^?, I^?, ClO₄ ^?, NO₃ ^?, and HSO₄ ^? anions. Sensor 2 shows color change upon interaction with F^?. Interactions of 1, 2 and 3 with F^? cause a red-shift in UV–vis absorption and a large Stokes shift in fluorescence emission due to the inhibition of ESIPT induced by the deprotonation of phenolic proton by F^?.     

Hypervalent silicon versus carbon: ball-in-a-box model

Why is silicon hypervalent and carbon not? Or why is [Cl? CH₃? Cl]^? labile with a tendency to localize one of its axial C? Cl bonds and to largely break the other one, while the isostructural and isoelectronic [Cl? SiH₃? Cl]^? forms a stable pentavalent species with a delocalized structure featuring two equivalent Si? Cl bonds? Various hypotheses have been developed over the years focusing on electronic and steric factors. Here, we present the so‐called ball‐in‐a‐box model, which tackles hypervalence from a new perspective. This model reveals the key role of steric factors and provides a simple way of understanding the above phenomena in terms of different atom sizes. Our bonding analyses are supported by computation experiments in which we probe, among other things, the shape of the S_N2 potential‐energy surface of Cl^? attacking a carbon atom in the series of substrates CH₃Cl, ^.CH₂Cl, ^..CHCl, and ^...CCl. Our findings for ClCH₃Cl^? and ClSiH₃Cl^? are generalized to other Group 14 central atoms (Ge, Sn, and Pb) and axial substituents (F).     

Structural and fluorescence properties of phenolphthalein bridged cyclotriphosphazatrienes

This study dealt with the reactions of hexachlorocyclotriphosphazatriene, N₃P₃Cl₆ (trimer) (1) with phenolphthalein (2) to give the phenolphthalein bridged compounds 3, 4 and 5. The phenolphthalein bridged cyclotriphosphazatriene derivatives are reported for the first time. The new compounds (3–5) are characterized by elemental analysis, mass spectrometry, UV–vis, FT-IR, ¹H, ³¹P NMR and fluorescence spectroscopy. The more bridged phenolphthalein groups show the higher intensity of the absorption bands in the UV–vis spectra. Fluorescence spectrum of compound 3 shows a small band in the lower spectral range, while the spectra of compounds 4 and 5 show more intense and a band in higher spectral range.     

Übergangsmetall-carben-Komplexe. LXXX. α-Alkoxy- und α,α-dialkoxysubstituierte Phenylacetyl-(pentacarbonyl)metallate und Pentacarbonyl[alkoxy(benzyl)-carben]-Komplexe des Chroms und Wolframs

Vibrational Spectra of Dichlorophosphorylmethylamine CH₃? NH? P(?O)Cl₂ and its Adducts with SbCl₅ and SnCl₄ The vibrational spectra of liquid samples and solutions, as well as cryoscopic molecular weight determinations show that CH₃? NH? P(?O)Cl₂ exists largely in the dimeric form. The association occurs through hydrogen bridges. The adducts SbCl₅ · CH₃? NH? P(?O)Cl₂ and SnCl₄ · 2 CH₃? NH? P(?O)Cl₂ are formed through addition via an oxygen atom. The ligands have cis-configuration in the tin compound.     

Coordination chemistry of bis(2-pyridylimine) ligands with Ag(I): formation of two structurally different coordination polymers and one metallocycle controlled by linker and the solvent system

Reaction of equimolar amounts of AgClO₄ and bis[4-(2-pyridylmethyleneamino)phenyl] methane (L¹) or bis[4-(2-pyridylmethyleneamino)phenyl] ether (L²) in a 1:1 solvent mixture of CH₃CN and CH₂Cl₂ leads to the formation of two infinite coordination polymers of the composition {[Ag(L¹)]ClO₄·CH₃CN}_n (1) and {[Ag(L²)]ClO₄·CH₂Cl₂}_n (2). Whereas 1 represents a homochiral single-stranded helicate the related complex 2 shows a typical zigzag chain arrangement. Both structures are characterized by a distorted tetrahedral coordination environment of the Ag(I) centres each based on a N₄ coordination pattern of two ligand molecules. The resulting strands are connected by a hydrogen bonding network including ClO₄ ^? anions and solvent molecules forming 2-D layers. Additional ?ШC?? and CH?C?? interactions between the aromatic parts of the ligand molecules give a 3-D arrangement of the packing. In contrast, a discrete dinuclear metallocycle, [Ag₂(L²)₂](ClO₄)₂·CH₃OH (3), has been formed by reaction of AgClO₄ with L² when CH₂Cl₂ in the solvent mixture was replaced by CH₃OH. Again each Ag(I) has a distorted tetrahedral geometry and is coordinated to two pyridylimine units of two ligand molecules. Additional weak hydrogen bonds involving perchlorate and solvent molecules as well as edge-to-face and face-to-face ?ШC?? interactions allow a 3-D packing arrangement.     

121Sb-Mößbauer-Spektren. IV. Benzamidinkomplexe des Antimon(V) Die Kristallstruktur von [Ph2Cl2Sb(N2Me2CPh)]

¹²¹Sb Mössbauer Spectra. IV. Benzamidine Complexes of Antimony(V). Crystal Structure of [Ph₂Cl₂Sb(N₂Me₂CPh)] The ¹²¹Sb Mössbauer spectra of the octahedral benzamidine complexes [Cl₄Sb[BAN)]] ( I ), [Ph₂Cl₃Sb(BAN)] ( II ), [Ph₂Cl₂Sb(BAN)] ( III ), and [Ph₃ClSb(BAN)] ( IV ) (BAN = N,N′-dimethyl-benzamidine) were measured at 4.2 K. The configuration of the complexes II–IV is derived from the values of the quadrupol split. In II the phenyl group is arranged in the axis, III contains both phenyl groups in equatorial position, located in trans-position to the N atoms of the chelate ligand, whereas in IV one phenyl group is placed axially, the other two are in equatorial position. The measurements are supplemented by the vibrational spectra below 600 cm^?1. Complex III crystallizes in the monoclinic space group P2₁/c with four formula units per unit cell. In addition, four molecules of CCl₄ per unit cell are placed in cavities of the lattice. The refinement has been carried on to an R-value of 6.5%, taking into account 1 729 unique, observed reflexions. The structure consists of discrete molecules of [Ph₂Cl₂Sb(N₂Me₂CPh)], in which the antimony atoms are surrounded by the N atoms of the chelate ligand, the phenyl groups and the two axial Cl atoms in distorted octahedral arrangement. The planes of the phenyl rings form dihedral angles with the equatorial plane of 129° and 143°.     

The mass spectral fragmentation of phenyl ω-dialkoxyethyl tellurides

The 70 eV mass spectrum of phenyl ω-dimethoxyethyl telluride [C₆H₅? Te? CH₂CH(OR)₂, R?CH₃]contains an intense peak at m/z 238 which corresponds to a rearrangement ion [C₆H₅? Te? OR]⁺. The formation of this species is further illustrated by the presence of a peak at m/z 241 in the spectrum of the hexadeuterated analog (R?CD₃) and a peak at m/z 252 in the spectrum of the ethyl analog (R?CH₂CH₃). These combined results illustrate the presence of only one of the alkoxyl groups in the rearrangement ion. Several other abundant ions that contain oxygen but not tellurium are present in the spectra of these compounds. High resolution analyses have aided in the determination of the origin and composition of several of the characteristic ions formed upon electron impact fragmentation of phenyl ω-dimethoxyethyl telluride.     

Ring-opening polymerization of ethylene organophosphorothioates: Stereoregular polymerization involving asymmetry at phosphorus

Stereoregular polymerization involving asymmetry at phosphorus has been obtained from ethylene methyl or phenyl phosphorothioate with R₂Mg? NH₃ catalysts, or, in some cases, with R₂Mg alone. The methyl ester gave two types of polymer: an amorphous rubber and a low-melting (75°C) crystalline polymer. The phenyl ester gave mainly a low-melting (68°C) crystalline polymer of 2.2 inherent viscosity. Proton and ³¹P NMR and infrared spectra of these polymers are in accord with the expected chain unit, ? CH₂CH₂? O? P(S)(OR)? O? . The polymerization mechanism probably involves an anionic ring-opening step with P? O cleavage. Ring opening with C? O cleavage appears to be largely excluded. This conclusion is based on the expectation that anionic ring opening with C? O cleavage should lead to a rearranged chain unit, ? CH₂CH₂? O? P(O)? (OR)? S? , because of the high nucleophilicity of sulfur as compared with oxygen. Proton and ³¹P NMR spectra give no evidence for the rearranged unit within the limit of detection (ca. 3%). However, on aging, the methyl ester polymer changes drastically to form up to 40% CH₂SP groups. Presumably, the polymer undergoes the well-known thiono-thiolo rearrangement characteristic of simple phosphorothioate esters to form ? CH₂CH₂? O? P(O)(SCH₃)? O? chain units. The phenyl ester polymer is stable under the same aging conditions.     

Beiträge zur Chemie der Silicium–Stickstoff-Verbindungen. CXXX. Kernresonanz- und infrarotspektroskopische Untersuchungen an Methylaminosilanen

Chemistry of Silicon-Nitrogen Compounds. CXXX. N.M.R. and I.R. Spectroscopic Investigations on Methylaminosilanes The attachment of a silicon atom to methylamino groups leads in the pure compounds I to VII to a HNCH coupling constant for the protons of J = 6–7 Hz. A similar effect is also observed in solution, except in CH₂Cl₂ and CHCl₃. The correct assignment of the n.m.r. signals for IV is shown in Fig. 1. I to VII have practically the same basic properties as can be concluded from the invariable shift of the C? D stretching vibration of 35 cm^?1 for CDCl₃.     

Mass spectometry of aralkyl compounds with a functional group—VI1: Mass spectra of 1-phenylethyanol-1, 2-phenylethanol-1 and 1-phenylpropanol-2

Mass spectra of 1-phenylethanol-1 and its analogues, specifically deuterated in the aliphatic chain, suggest that the [M? CH₃]⁺ ion is represented partly by an α-hydroxybenzyl fragment. Moreover, the molecular ion loses successively—after scrambling of all hydrogen atoms, except those of CH₃? a hydrogen atom and C₆H₆, generation the CH₃CO⁺ ion. Diffuse peaks, found in the spectra of of 2-phenylethanol-1 and its analogues, specifically deuterated in the aliphatic chain and in the phenyl ring, show that the molecular ion loses C₂H₄O, possibly via a four-center mechanism, after an exchange of aromatic and hydroxylic hydrogens. Mass spectra of 1-phenylpropanol-2 and its analogues, specifically, deuterated in the aliphatic chain, demonstrate that in the molecular ion exclusively the hydroxyl hydrogen atom is transferred to one of the ortho-positions of the phenyl ring via a McLafferty rearrangement, generating the [M ? C₂H₄O]⁺ ion. Furtherore, an eight-membered ring structure is proposed for the [M ? CH₃]⁺ ion to explain the loss of H₂O and C₂H₂O from this ion after an extensive scrambling of hydrogen atoms.     

3,3′-bis(dipyrrolylmethenes) as new chelating ligands: Synthesis and spectral properties

Hydrobromides of three new alkyl-substituted tetrapyrrole ligands with an open chain, in which the dipyrrolylmethene fragments are linked by a CH₂-spacer at the 3,3′-pyrrole carbon atoms, were synthesized and studied by IR, ¹H NMR, and electronic absorption spectroscopy. As compared to the 2,2′ isomers (alkyl derivatives of biladiene-a,c) and monomers (2,2′-, 2,3′-, and 3,3′-dipyrrolylmethenes, the effect of structural factors is manifested in a considerable (up to 19–31 nm) bathochromic shift of the strong band in the electronic spectrum, an increase in the N-H stretching vibration frequency in the IR spectra (by more than 30 cm^?1), and a decrease in the stability of 3,3′-bis(dipyrrolylmethene) salts. The solvent effect is manifested in small changes in the quantitative characteristics of the electronic absorption spectra of 3,3′-tetrapyrrole hydrobromides in C₆H₆, CCl₄, CH₂Cl₂, CHCl₃, and alcohols. In DMF, DMSO, and C₅H₅N, the salts undergo solvolytic dissociation to the free ligands and HBr, which accelerates in dilute solutions (<10^?4 M) and with an increase in the electron-donor power of the solvent. The auxochromic effects of protons in the electronic absorption spectra of the salts, compared to ligands, were estimated quantitatively.     

Synthesis and electrochemical properties of calix[4]arene derivatives containing ferrocene units in the cone and 1,3-alternate conformation

Two novel calix[4]arene receptors containing ferrocene units in cone (L₁) and 1,3-alternate (L₂) conformations have been synthesized from 25,27-dihydroxy-26,28-bis[(3-aminopropyl)oxy]calix[4]arene 4 or 25,26,27,28-tetra[(3-aminopropyl)oxy]calix[4]arene 6 and ferrocenecarboxaldehyde via condensation, respectively. Their structures have been characterized by ¹H, ¹³C, APT, COSY NMR, FTIR, HSMR, and UV–vis spectral data. The electrochemical behavior of L₁ and L₂ has been investigated in the presence of F^?, Cl^?, Br^?, H₂PO₄^?, CH₃COO^? anions. Electrochemical studies show that these receptors electrochemically recognize CH₃COO^?, H₂PO₄^?, and Cl^?, anions. Using an UV–vis study, the selectivity to these anions in DMSO solution was confirmed.     

‘Naked-eye’ detection of F− ions by two novel colorimetric receptors

Two novel colorimetric receptors, S1 and S2, linked to one or two nitrophenylurea groups were synthesized in good yields, characterized and their chromogenic properties investigated towards various anions (F^?, Cl^?, Br^?, I^?, NO₃^?, AcO^?, ClO₄^?, HSO₄^?, and H₂PO₄^?) by UV–vis and ¹H NMR techniques. The receptors, effectively and selectively, recognized and distinguished the biologically important F^? from other anions such as Cl^?, Br^?, I^? etc. in CH₃CN. This selectivity could be easily observed by the naked eye, indicating that receptors S1 and S2 are potential colorimetric sensors for fluoride ion.     

Bildung und NMR-spektroskopische Charakterisierung von Alk-(ar-)oxyderivaten von Trichlorphosphazen-N-phosphoryldichlorid,Cl3PN?P(O)Cl2, Imido- und N-Methylimidodiphosphoryltetrachlord,Cl2P(O)NHP(O)Cl2 bzw. Cl2P(O)N(CH3)P(O)Cl2

Formation and N.M.R.-Spectroscopic Characterization of Alk-(ar-)oxy Derivatives of Trichlorophosphazene-N-phosphoryldichloride, Cl₃P?N? P(O)Cl₂, Imido- and N-Methylimidodiphosphoryltetrachloride, Cl₂P(O)NHP(O)Cl₂ and Cl₂P(O)N(CH₃)P(O)Cl₂ The ester chlorides and esters P₂NOCl_5?x(OR)_x (x = 1?5), P₂(NH)O₂Cl_4?x(OR)_x (x = 1–4) and P₂(NCH₃)O₂Cl_4–x(OR)_x (x = 1–4) derived from the title compounds by substitution of chlorine atoms by alk- or aroxy groups are characterized by their ³¹P-n.m.r. data. The possibilities for forming these compounds by alcoholysis, chloridolysis, dealkylation and P? N-bond formation are discussed.