Critical role of H-aggregation for high-efficiency photoinduced charge generation in pristine pentamethine cyanine salts.

The mechanism of photoinduced symmetry-breaking charge separation in solid cyanine salts at the base of organic photovoltaic and optoelectronic devices is still debated. Here, we employ femtosecond transient absorption spectroscopy (TAS) to monitor the charge transfer processes occurring in thin films of pristine pentamethine cyanine (Cy5). Oxidized dye species are observed in Cy5-hexafluorophosphate salts upon photoexcitation, resulting from electron transfer from monomer excited states to H-aggregates.

Group 6 Hexacarbonyls as Ligands for the Silver Cation: Syntheses, Characterization, and Analysis of the Bonding Compared with the Isoelectronic Group 5 Hexacarbonylates.

The syntheses of the two novel complexes [Ag{Mo/W(CO) } ] [F-{Al(OR ) } ] (R =C(CF ) ) are reported along with their structural and spectroscopic characterization. The X-ray structure shows that three carbonyl ligands from each M(CO) fragment bend towards the silver atom within binding Ag-C distance range. DFT calculations of the free cations [Ag{M(CO) } ] (M=Cr, Mo, W) in the electronic singlet state give equilibrium structures with C symmetry with two bridging carbonyl groups from each hexacarbonyl ligand.

Cationic Niobium-Sandwich and Piano-Stool Complexes.

The syntheses of the homoleptic bis(arene) niobium cations [Nb(arene) ] (arene = C H Me , C H Me) with 16 valence electrons and heteroleptic arene-carbonyl cations [(CO)Nb(arene) ] (arene = C H Me , C H Me) and [(arene)M(CO) ] (arene = C H Me , C H ) obeying 18 valence electrons are described. Stabilization of these complexes was achieved by using the weakly coordinating anions [Al(OR ) ] or [F{Al(OR ) } ] (R = C(CF ) ). The limits of two synthesis routes starting from neutral Nb(arene) (arene = C H Me , C H Me) or [NEt ][M(CO) ] (M = Nb, Ta) were investigated.

Altering Charges on Heterobimetallic Transition-Metal Carbonyl Clusters.

The homoleptic group 5 carbonylates [M(CO) ] (M=Nb, Ta) serve as ligands in carbonyl-terminated heterobimetallic Ag M clusters containing 3 to 11 metal atoms. Based on our serendipitous [Ag {Nb(CO) } ] (4 a ) precedent, we established access to such Ag M clusters of the composition [Ag {M(CO) } ] (M=Nb, Ta; m=1, 2, 6; n=2, 3, 4, 5; x=1-, 1+, 2+). Salts of those molecular cluster ions were synthesized by the reaction of [NEt ][M(CO) ] and Ag[Al(OR ) ] (R =C(CF ) ) in the correct stoichiometry in 1,2,3,4-tetrafluorobenzene at -35 °C.

Why Do Five Ga Cations Form a Ligand-Stabilized [Ga ] Pentagon and How Does a 5:1 Salt Pack in the Solid State?

The reaction of the Ga source [Ga(PhF) ] [Al(OR ) ] with the neutral σ-donor ligand dmap (4-Me N-C H N) produces the unexpectedly large and fivefold positively charged cluster cation salt [Ga (dmap) ] ([Al(OR ) ] ) . It includes a regular and planar Ga pentagon with strong metal-metal bonding. Additionally, the compound represents the first salt in which an ionic 1:5 packing is realized.

Isolation of a stable pyridine radical anion.

Reduction of 2,6-bis(diazaboryl)pyridine with KC8 gives a room-temperature-stable yellow colored solution containing the corresponding radical anion. The radical was characterized by single crystal XRD, EPR spectroscopy, UV-vis absorption spectroscopy and electrochemically, supported by theoretical calculations. The negative charge and spin density are mainly distributed over the atoms of the pyridine ring, making this the first isolated pyridine radical anion as its potassium salt.

Development, Scope, and Applications of Titanium(III)-Catalyzed Cyclizations to Aminated N-Heterocycles.

The exceptionally mild conditions of a titanium(III)-catalyzed cyclization reaction paired with a convenient acid/base extraction have enabled the straightforward synthesis, isolation, and direct N-functionalization of amino heterocycles such as 3-aminoindoles and -pyrroles. The unprotected heterocycles are ideal building blocks for the installation of aminated indoles and pyrroles into target molecules, but their sensitivity has previously impeded their synthesis by modern catalytic methods. This full paper presents the development and extended scope of the new cyclization methodology.

A Unified Approach to Customized Chiral Carbon-Bridged ansa-Metallocenes.

Chiral ansa-metallocenes are privileged catalysts for a range of stereoselective transformations. Their synthesis, however, has remained a tremendous challenge, which has prevented a broad and systematic exploration for applications in synthesis and catalysis. A modular approach to such ansa-metallocenes that enables a facile modification of the ring substitution and the ligand bridge, as well as the introduction of various core metals, is described.

Tetracationic Gallium Cluster Cations.

The univalent salt Ga(PhF) [Al(OR ) ] (R =OC(CF ) ) forms the strongly metal-metal bonded cluster tetracations [Ga (L) ] and [Ga (L') ] , when it reacts with innocent ligands like phenanthroline (L=phen) or t-butylisonitrile (L'= Bu-NC). Their structures and energetics are discussed as a function of the employed ligands, supported by DFT calculations and Born-Fajans-Haber cycles.

The perfluorinated alcohols c-CFOH, c-CF-1,1-(OH) and c-CF-1-(CF)OH.

The thermally unstable α-fluoroalcohol undecafluorocyclohexanol (c-C6F11OH) was prepared by addition of hydrogen fluoride to the corresponding ketone. c-C6F10(CF3)OH was obtained by protonation of its alkoxide [NMe4]+[C7F13O]-. Decafluorocyclohexane-1,1-diol (c-C6F10(OH)2) was prepared by acidic workup of the corresponding alkoxide [NMe4]+[C6F11O]- with sulfuric acid, which yielded (c-C6F10(OH)2) and fluorosulfonic acid.

Access to the Bis-benzene Cobalt(I) Sandwich Cation and its Derivatives: Synthons for a "Naked" Cobalt(I) Source?

The synthesis and structural characterization of the hitherto unknown parent Co(bz) (bz=benzene) complex and several of its derivatives are described. Their synthesis starts either from a CoCO salt, or directly from Co (CO) and a Ag salt. Stability and solubility of these complexes was achieved by using the weakly coordinating anions (WCAs) [Al(OR ) ] and [F{Al(OR ) } ] {R =C(CF ) } and the solvent ortho-difluorobenzene (o-DFB).

Dibenzo[a,e]pentalenophanes: Bending a Non-Alternant Hydrocarbon.

In cyclophanes, an aromatic moiety is incorporated into a (strained) cyclic structure. Of particular interest as model systems for bent carbon nanostructures are those containing polycyclic aromatic hydrocarbons. Dibenzo[a,e]pentalene (DBP) is a non-alternant polycyclic hydrocarbon with small band gap and tunable optoelectronic properties.

Dibenzo[a,e]pentalenes with Low-Lying LUMO Energy Levels as Potential n-Type Materials.

Ambipolar organic semiconductors are of high interest for organic field-effect transistors. For n-type conduction, low LUMO energies are required. Dibenzo[a,e]pentalenes (DBPs) are promising compounds; however, few derivatives exist with energetically low-lying LUMO levels.

Synthesis, Characterisation and Reactions of Truly Cationic Ni -Phosphine Complexes.

The recently published purely metallo-organic Ni salt [Ni(cod) ][Al(OR ) ] (1, cod=1,5-cyclooctadiene, R =C(CF ) ) provides a starting point for a new synthesis strategy leading to Ni phosphine complexes, replacing cod ligands by phosphines. Clearly visible colour changes indicate reactions within minutes, while quantum chemical calculations (PBE0-D3(BJ)/def2-TZVPP) approve exergonic reaction enthalpies in all performed ligand exchange reactions. Hence, [Ni(dppp) ][Al(OR ) ] (2, dppp=1,3-bis(diphenylphosphino)propane), [Ni(dppe) ][Al(OR ) ] (3, dppe=1,3-bis(diphenyl-phosphino)ethane), three-coordinate [Ni(PPh ) ][Al(OR ) ] (4) and a remarkable two-coordinate Ni phosphine complex [Ni(PtBu ) ][Al(OR ) ] (5) were characterised by single crystal X-ray structure analysis.

Two synthetic approaches for the preparation of tin(ii) dications.

Examples of tin dications without closer contacts to the anion are rare, as are straightforward routes to weakly coordinated tin(ii) dication salts. Here we report on the synthesis of [Sn(MeCN)][Al(OR)] (R = C(CF)) via NO-oxidation of tin metal. Subsequently, [Sn(MeCN)][Al(OR)] was used to prepare the mixed coordinated [Sn(pyr)(MeCN)][Al(OR)] and [Sn(PPh)-(MeCN)][Al(OR)]·MeCN.

From an Easily Accessible Pentacarbonylcobalt(I) Salt to Piano-Stool Cations [(arene)Co(CO) ].

The facile synthesis of a pentacarbonyl cobalt(I) salt without the need for a superacid as solvent is presented. This salt, [Co(CO) ] [Al(OR ) ] {R =C(CF ) }, readily accessible on a multigram scale, undergoes substitution reactions with arenes yielding the hitherto unknown class of two-legged cobalt piano-stool complexes [(arene)Co(CO) ] with four different arene ligands. Such a substitution chemistry would have been impossible in superacid solution, as the arenes used would have been oxidized and/or protonated.

Using the Lewis Acid Me Si-F-Al(OR ) To Prepare Phosphino-Phosphonium Cations with the Least-Coordinating Anion [(R O) Al-F-Al(OR ) ].

By reaction of two equivalents of Me Si-F-Al(OR ) 1 with an equimolar amount of PPh Cl, the salt [Ph P-PPh Cl] [(R O) Al-F-Al(OR ) ] 2 is prepared smoothly in 91 % yield (NMR, XRD). The synthesis of [Ph P-PPh ] [(R O) Al-F-Al(OR ) ] 3 is best achieved by a two-step reaction: first, two equivalents of 1 react with one PPh to give [Me Si-PPh ] [(R O) Al-F-Al(OR ) ] 4 (NMR, XRD), which, upon reaction with PPh Cl, yields pure 3 and Me SiCl (NMR, XRD). Typically, a stoichiometry of two equivalents of 1 with respect to one equivalent of the chloride donor should be used.

The Parent Cyclopentadienyltin Cation, Its Toluene Adduct, and the Quadruple-Decker [Sn Cp ].

Truly cationic metallocenes with the parent cyclopentadienyl ligand are so far unknown for the Group 14 elements. Herein we report on an almost "naked" [SnCp] cation with the weakly coordinating [Al{OC(CF ) } ] and [{(F C) CO} Al-F-Al{OC(CF ) } ] anions. [SnCp][Al{OC(CF ) } ] was used to prepare the first main-group quadruple-decker cation [Sn Cp ] again as the [Al{OC(CF ) } ] salt.

Light- or oxidation-triggered CO release from [Mn(CO)(κ-L)] complexes: reaction intermediates and a new synthetic route to [Mn(μ-O)(L)] compounds.

The reaction products and intermediates of the three CO-releasing manganese(i) coordination compounds [Mn(tpm)(CO)], [Mn(bpza)(CO)] and [Mn(tpa)(CO)] were analysed by combining IR-spectroscopy, electrochemical measurements and single-crystal XRD. The intermediate formation of manganese(i) biscarbonyl compounds and the rather facile oxidation of these species were identified as key reaction steps that accompany CO liberation. For the use of [Mn(CO)] complexes as light-triggered CO sources, the results indicate that in this case photo- and redox-chemistry seem to be strongly coupled which could be important and potentially even useful in the pharmacological context.

Homoleptic Gold Acetonitrile Complexes with Medium to Very Weakly Coordinating Counterions: Effect on Aurophilicity?

A series of gold acetonitrile complexes [Au(NCMe) ] [WCA] with weakly coordinating counterions (WCAs) was synthesized by the reaction of elemental gold and nitrosyl salts [NO] [WCA] in acetonitrile ([WCA] =[GaCl ] , [B(CF ) ] , [Al(OR ) ] ; R =C(CF ) ). In the crystal structures, the [Au(NCMe) ] units appeared as monomers, dimers, or chains. A clear correlation between the aurophilicity and the coordinating ability of counterions was observed, with more strongly coordinating WCAs leading to stronger aurophilic contacts (distances, C-N stretching frequencies of [Au(NCMe) ] units).

Cationic cluster formation versus disproportionation of low-valent indium and gallium complexes of 2,2'-bipyridine.

Group 13 M(I) compounds often disproportionate into M(0) and M(III). Here, however, we show that the reaction of the M(I) salt of the weakly coordinating alkoxyaluminate [Ga(I)(C6H5F)2](+)[Al(OR(F))4](-) (R(F)=C(CF3)3) with 2,2'-bipyridine (bipy) yields the paramagnetic and distorted octahedral [Ga(bipy)3](2+)(•){[Al(OR(F))4](-)}2 complex salt. While the latter appears to be a Ga(II) compound, both, EPR and DFT investigations assign a ligand-centred [Ga(III){(bipy)3}(•)](2+) radical dication.

[Ni(cod)2][Al(OR(F))4], a Source for Naked Nickel(I) Chemistry.

The straightforward synthesis of the cationic, purely organometallic Ni(I) salt [Ni(cod)2](+)[Al(OR(F))4](-) was realized through a reaction between [Ni(cod)2] and Ag[Al(OR(F))4] (cod = 1,5-cyclooctadiene). Crystal-structure analysis and EPR, XANES, and cyclic voltammetry studies confirmed the presence of a homoleptic Ni(I) olefin complex. Weak interactions between the metal center, the ligands, and the anion provide a good starting material for further cationic Ni(I) complexes.

: enhanced modelling and refinement of disordered structures with .

One of the remaining challenges in single-crystal structure refinement is the proper description of disorder in crystal structures. This paper describes a computer program that performs semi-automatic modelling of disordered moieties in [Sheldrick (2015 ▶). C, 3-8.