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The transient photoconducting behavior of organic p/n bilayer photocells has been investigated in cells constructed with the copolymer, poly(3-butylthiophene-co-ethylenedioxythiophene), as p-type material and a perylene diimide (PV) as the n-type material. The decay rate constant of the transient photocurrent observed after pulsed illumination is independent of the applied electric field, light intensity, and temperature. However, the peak photoresponse was strongly affected by these variables. Simulations of the photoresponse revealed that the peak current depends primarily on the carrier mobility (at a given light intensity), whereas the characteristic decay rate is hardly influenced by the mobility, but depends on the carrier lifetime which is chiefly due to trapping by deep levels.

The oxidative behavior of bithiazole-ethylenedioxythiophene co-oligomers is described. The acceptor−donor−acceptor (A−D−A) compounds, 5,5‘-bis(4,4‘-dialkyl-2,2‘-bithiazol-5-yl)-(3,4,3‘,4‘-bis(ethylenedioxy)-2,2‘-dithienyl) (1, 2), are sequentially oxidized by NOBF4 through the paramagnetic monocation to the diamagnetic dication. The monocations form diamagnetic π-dimers, the allowed π−π electronic transitions of which are interpreted in terms of molecular exciton theory to give nearest-neighbor exciton coupling constants, J ≅ 0.2 eV. The spectra of the dications show that they are bipolarons; that is, the two charges share a common lattice deformation. The D−A−D co-oligomers, 5,5‘-bis(3,4-ethylenedioxythien-2-yl)-4,4‘-dibutyl-2,2‘-bithiazole (3) and 5,5‘-bis(3,4,3‘,4‘-bis(ethylenedioxy)-2,2‘-dithien-5-yl)-4,4‘-dibutyl-2,2‘-bithiazole (4), are oxidized in a single step to the corresponding bipolarons.

Photoconduction of bilayer organic p/n junction photocells can be finely tuned through the alteration of either the side chain orientation (regiorandom vs regioregular) or main chain structure in poly(3-alkylthiophene)s (P3ATs), where the incorporation of an electron-donating group (EDOT) appears to be an excellent method for enhancing the photoconduction. Moreover, doping of P3ATs proved to be an equally viable route for tuning the device characteristics. These polymers were used to fabricate bilayer organic photocells with the polymer as the p-type layer and 1,2-diaminobenzene perylene-3,4,9,10-tetracarboxylic acid diimide (PV) as the n-type layer. Action spectra at steady-state illumination demonstrated that all the interfaces (organic−organic p/n junction and organic−electrode) are actively involved in the photogeneration of carriers. Experiments showed that critical device properties, for example, open-circuit voltage (Voc) and short-circuit current (Isc), are not only dependent on the selection of electrodes and organic materials but also greatly affected by the illumination wavelength and intensity.

The synthesis and characterization of several co-oligomers, 5,5‘-bis(4,4‘-dialkyl-2,2‘-bithiazol-5-yl)-(3,4,3‘,4‘-bis(ethylenedioxy)-2,2‘-dithienyl) (AT2A), 5,5‘-bis(3,4-ethylenedioxythien-2-yl)-4,4‘-dibutyl-2,2‘-bithiazole (TBT), and 5,5‘-bis(3,4,3‘,4‘-bis(ethylenedioxy)-2,2‘-dithien-5-yl)-4,4‘-dibutyl-2,2‘-bithiazole (T2BT2) are described. The solid-state structure of AT2A features π-stacking with a short intermolecular distance of 3.5 Å. In thin films, the π-stacks are parallel to the film substrate as determined by X-ray diffraction. The UV−vis spectra of AT2A films show features that are ascribed to the effects of π-stacking. In addition, all these co-oligomers, composed of donor−acceptor moieties, show lowered optical band gaps, mainly because of the low oxidation potential imparted by incorporation of the 3,4-ethylenedioxythiophene (EDOT) moiety. Cyclic voltammetry indicates that these co-oligomers can be either p-doped or n-doped, and the spectroelectrochemical measurements show that the AT2A films are stable upon cycling the oxidation state. All these features make these materials promising for use in electronic devices, e.g., organic thin film transistors.

Synthesis and characterization of poly(thiophene)s with pendant vinylene ferrocene (Fc) or cyanovinylene ferrocene units are described. Charge-transfer (CT) effects between the Fc groups and the conjugated polymer backbone have been demonstrated by the substantial photoluminescence (PL) quenching and spectroelectrochemistry. J−V studies on p/n bilayer devices (ITO/polymer/perylene imide (PV)/Ag) show significant photoconductance improvement when Fc concentration reached ~40 mol % where short-circuit current density, Jsc, was increased 70% as compared to a similar ITO/P3BT/PV/Ag device.

The head−tail (HT) sequence length distributions (SLDs) of poly(3-alkylthiophenes) (P3ATs) and related polymers may be obtained from the H NMR spectra. The results show that the regioregular polymers, i.e., those with the highest HT content, have broader SLDs than the less regular polymers. The SLD may be used to simulate the characteristic profiles of the π−π* absorption peaks of P3ATs and related polymers.

Addition of the configurationally stable organolithium species produced by enantioselective deprotonation of N-Boc-N-(p-methoxyphenyl) allylamines to α,β-unsaturated carbonyl compounds affords 1,4-addition products in good yields with high diastereomeric and enantiomeric ratios. Further transformations of these compounds provide [3.3.0]-, [4.3.0]-, [5.3.0]-, and [5.4.0]-carbocycles and heterocycles with high stereoselectivities.

Bis(alkylcyclopentadienyl)arenes have been prepared by sequential lithiation/alkylation of dibromoarenes with alkylcyclopenta-2-en-1-ones. The resulting dicarbinols were dehydrated with p-toluenesulfonic acid to give the bis(alkylcyclopentadienyl)arene. Poly(alkyl-1,1‘-ferrocenylenearylene)s were prepared by the reaction of dilithio bis(alkylcyclopentadienide)arenes and iron(II) salts in THF. The resulting polymers were oxidized with iodine to give the fully oxidized polyionomers. The polyionomers were found to give mixed-valence polymers when allowed to equilibrate with neutral polymers in solution, provided the degree of oxidation, N, lies between ca. 0.55 and 1.0. For degrees of oxidation 0.0 < N <0.55, disproportionation occurs to give neutral polymer and polymer with N ≈ 0.55. The oxidized polymers showed small to moderate antiferromagnetic interactions, and some were found to follow non-Curie−Weiss behavior that is ascribed to the complex magnetic properties of individual ferrocenium centers rather than to any type of magnetic ordering. The organic bridging ligands and polymers were characterized by TGA-DSC, GPC, NMR, CV, FT-IR, and UV−vis techniques. The fully oxidized and mixed-valence polymers were characterized by magnetic susceptibility, FT-IR, EPR, Mössbauer, and UV−vis spectroscopies.

A theoretical foundation, tools for recognition and control, and recent examples of a class of asymmetric transformation termed dynamic thermodynamic resolution are presented. Enantioselective reaction pathways that involve an induced diastereomeric equilibration to intermediates, which are configurationally stable on the time scale of a subsequent reaction, are illustrated. Dynamic thermodynamic resolution differs from the classic, well-documented pathways of kinetic resolution and dynamic kinetic resolution in that equilibration and resolution can be operative on one system in separate controllable steps. This approach offers a high level of flexibility and provides multiple opportunities for optimization of enantioselectivity.

The synthesis of poly(4,4‘-dinonyl-2,2‘-bisoxazole-5,5‘-diyl) (PNBO) was performed through a nickel-mediated coupling of 5,5‘-dibromo-4,4‘-dinonyl-2,2‘-bisoxazole. The solid-state morphology of PNBO was determined by powder X-ray diffraction (XRD) which showed strong peaks due to lamellar spacing and three-dimensional ordering. The polymer has absorbance maxima of 446 and 464 nm in solution, and 475 nm in the film. A low wavelength shoulder near 510 nm is ascribed to the absorption of aggregated molecules. The emission spectra are concentration dependent and consistent with emission from excimers. Essentially all the emission in the solid state is due to excimers. The physical and chemical properties of PNBO are compared to the sulfur analogues, poly(4,4‘-dinonyl-2,2‘-bithiazole-5,5‘-diyl) (PNBTz) and poly(3-alkylthiophene)s.

The syntheses of the 1,4-bis-5-(4,4‘-dialkyl-2,2‘-bithiazole)-1,3-butadiynes, ABDs, (6a−c) are reported. The crystal and molecular structure of the butyl derivative was determined by single-crystal X-ray diffraction. The BBD (the 4,4‘-di-n-butyl ABD) molecules are properly aligned in the solid state for topotactic 1,4-polymerization to occur, but these materials do not undergo such polymerization under a variety of conditions. The lack of topotactic polymerization is attributed to the rigidity of the aromatic groups directly bonded to the butadiyne. These compounds do polymerize in the molten state to give soluble polymers that are characterized by UV−vis, FT-IR, and NMR spectroscopies and cyclic voltammetry. Molecular modeling was also used to explore some representative conformation space. These data suggest that the polymerization occurs primarily via 1,2-addition, but some 1,4-addition also occurs.

The N-atoms in two polymers, poly(4,4‘-dinonyl-5,5‘-bithiazole-2,2‘-diyl-co-5-tert-butylphenylene-1,3-diyl) (PBT) and poly(4,4‘-bis(p-dodecylphenyl)-2,2‘-bithiazole-5,5‘diyl) (DBT), have been quaternized by the reaction of the polymer with methyltriflate to give their respective N-methylated derivatives, MPBT and MDBT. Quaternization of the ring nitrogen atom lowers the energy levels of both the HOMO and LUMO and, hence, alters those polymer properties which are dependent on these energy levels. Both the absorbance and emission spectra red shift upon methylation, and the electrochemical reduction potential increases by 0.88 V. An increase of up to 8 orders of magnitude was also observed in the conductivity.

The synthesis and characterization of 4,4‘-dinonyl-2,2‘-bisoxazole (NBO) and its oligomers are described. The optical, electronic, and structural properties of these oligomers, NBO, NBO2, and NBO3, are compared to their sulfur analogues (NBT, NBT2, and NBT3). In the series (NBO)n and (NBT)n, there is a red shift in the λmax as “n” increases. This effect is observed in both the solid and solution states. The bithiazole oligomers have longer wavelength absorbances than those of the bisoxazole oligomers; however, the observed red shift is greater as “n” increases for the bisoxazole oligomers leading to a merging of the absorption maxima between the two systems. The larger red shift for the bisoxazole series is explained by the larger atomic orbital coefficients at the coupling sites of the bisoxazole oligomers versus those of the bithiazole derivatives. Both systems exhibit thermochromic behavior corresponding to a transition from an ordered to disordered state. Upon heating, the bisoxazole system shows a gradual conformational change indicated by continual blue shifts of the absorption maximum. Conversely, the less rigid bithiazole system exhibits an immediate order−disorder transition upon heating evidenced by the appearance of an isosbestic point in the absorption spectrum. The solid-state packing of the n = 2 and 3 oligomers is very similar; however, the solid-state structures of NBO and NBT are different as determined by single-crystal X-ray diffraction. NBO packs in a two-layered “ribbonlike” structure, whereas NBT forms molecular stacks. The reduction potentials of (NBO)n increase (become more positive) from −2.97 to −2.60 to −2.46 V for n = 1, 2, and 3, respectively, and the number of reductions observed corresponds to the number of NBO units.

A series of new bimetallic sulfido clusters, Cp^#2M2M‘2S4(NO)2 (Cp^# = C5Me2Et, C5Me5, C5H5; M = Mo, W; M‘ = Fe, Co) have been synthesized and characterized by X-ray diffraction. Two new tungsten carbonyl clusters, Cp*2W2Co2S4(CO)2 and Cp^Et2W2Co2S3(CO)5, were also synthesized and the structure of the latter determined. The structural systematics are related to the redox properties and to the electronic structure of the clusters.

The paramagnetic cluster anions Cp‘2Mo2Co2S4(CO)2^- (6), and Cp*2Mo2Co2S4(CO)2^- (6*) were prepared by the reaction of Cp‘2Mo2Co2S3(CO)4 with p-toluene thiolate or by Na amalgam reduction of the cubane Cp*2Mo2Co2S4(CO)2 (Cp* = C5Me4Et), respectively. The CO-substituted cluster Cp‘2Mo2Co2S3(CO)3(SAr)^- (7) was a minor byproduct in the synthesis of 6. The X-ray crystal structures of these anionic clusters were determined. The effects of the addition or removal of electron density from the cluster core on the cluster structure is presented.

The intercalation of MoS2 with Co and Fe complexes has been accomplished via exfoliation of LixMoS2 by reaction with water, followed by flocculation in the presence of cationic guest species. The resulting self-assembled compounds have been characterized by X-ray absorption spectroscopy, electron diffraction, powder X-ray diffraction, and magnetic measurements. The 2H-type (undistorted) MoS2 undergoes a structural distortion to 1T-type MoS2 during the Li intercalation, which is partially maintained upon exfoliation and flocculation. A structural model of 1T-MoS2 is proposed on the basis of X-ray absorption spectroscopy and electron diffraction, in which the unit cell has P3 symmetry with lattice parameters a = 6.52(5) Å, c = 6.14 Å. The Mo atoms are shifted approximately 0.5 Å from their positions in 2H-MoS2 to form trigonal clusters in 1T-MoS2, with a concomitant change in coordination geometry from trigonal prismatic to distorted octahedral. Layers of Co(OH)2 were intercalated between the distorted and/or undistorted layers of MoS2 when either Co²⁺ or Co³⁺ complexes were used as the flocculating ion. Flocculation of exfoliated MoS2 with (η⁵-C5H5)2M⁺ (M = Fe, Co) resulted in intercalation of monolayers of the metallocenium cations between the partially negatively charged MoS2 sheets.

Three polymers, poly(4,4‘-dinonyl-5,5‘-bithiazole-2,2‘-diyl-co-5-tert-butylphenylene-1,3-diyl) (PBBNBT), poly(4,4‘-bis(p-dodecylphenyl)-2,2‘-bithiazole-5,5‘-diyl) (PDPBT), and poly(4,4‘-dinonyl-2,2‘-bithiazole-5,5‘-diyl-co-ethynylene) (PENBT), have been synthesized. These polymers illustrate the ability to tune polymer properties around a specific chromophore, in this case the bithiazole ring system. Alterations of optical properties and solid-state morphology have been made while the electrochemical behavior characteristic of the bithiazoles, i.e., reversible reduction near −2.0 V and n-dopability resulting in conductivities around 10² S/cm, has been maintained. All three polymers have also been used as the emitting layer in polymer-based LEDs.

A new coupling reaction based on the Pd-catalyzed reductive coupling of thienyl mercuric chlorides is described. A variety of substituted thiophenes react with HgCl2 to produce thienyl mercuric chlorides. The degree of substitution can be controlled by the choice of temperature, solvent, and reaction time, and the resulting chloromercuri thiophenes or bis(chloromercuri)thiophenes are stable to air and water. Heating the thienyl mercuric chlorides in pyridine solvent with Cu powder and PdCl2 catalyst gave good yields of the coupled thiophenes. Poly(alkyl)thiophenes, poly(alkyl thienylacetate esters), and copolymers of alkylthiophenes with unsubstituted thiophene were formed in good yields. Molecular weights, Mw, were in the range 5300−83000. This coupling reaction was demonstrated to be compatible with the presence of an electrophilic substituent that is attacked by more nucleophilic intermediates, e.g., thienyllithium or thienyl Grignard reagents. Thus, this synthesis should be compatible with substituents known to be unreactive toward arylmercuric chlorides or arylpalladium compounds and is therefore complementary to the organometallic coupling schemes currently in use.

Poly(thienylene ketone)s are formed by the copolymerization of bis(chloromercuri)thiophenes with carbon monoxide. The reaction is carried out in hot pyridine with a Pd catalyst under 500 psi of CO. The polymers, poly(3-methylthienylene ketone), poly(3-butylthienylene ketone), and poly(3-(carboethoxymethyl)thienylene ketone), with molecular weights, Mn, ranging from 1600 to 2700, were produced. The polymers have UV−vis absorption maxima near 360 nm, assigned to π−π* transitions, and are reduced irreversibly near −1.0 V vs SCE.

The heterobimetallic sulfido cluster Cp^Et2Mo2Co2S4(CO)2 was oxidized to give a series of 58-VSE (valence shell electron) electron-deficient clusters of the type Cp^Et2Mo2Co2S4(X)2 (X = I, Br, Cl, SPh). These clusters have been structurally characterized by X-ray diffraction. Their magnetic behavior was investigated to reveal complex spin equilibria for the halide-substituted clusters (X = I, Br, Cl) and simple paramagnetism for the thiolate substituted cluster (X = SPh). In an attempted catalytic reaction, Cp^Et2Mo2Co2S4(CO)2 reacted with excess benzene thiol under 1000 psi of CO at 150 °C to give phenylthiobenzoate, PhS(CO)Ph, and PhSSPh in excess of the stoichiometric amounts.

Treatment of the heterobimetallic sulfido cluster Cp‘2Mo2Co2S3(CO)4 (1) with the diphosphine compound bis(diphenylphosphino)methane (dppm) or bis(diphenylphosphino)ethane (dppe) gives the carbonyl-substituted adduct Cp‘2Mo2Co2S3(CO)2(η²-dppm) (11a) or Cp‘2Mo2Co2S3(CO)2(η²-dppe) (11b), respectively, whereas treatment of 1 with an excess of bis(dimethylphosphino)ethane (dmpe) gives the cluster Cp‘2Mo2Co2S3(μ3-CO)(η²-dmpe)2 (12) containing a triply-bridging carbonyl ligand (νCO = 1615 cm^-1). Cluster 12 readily reacts with dichloromethane to give the μ3-methylidyne cluster [Cp‘2Mo2Co2S3(μ3-CH)(η²-dmpe)2]⁺ (14). Cluster 14 was also characterized by an X-ray crystallographic analysis. Reaction of ¹³CO-labeled 12 with CH2Cl2 and CD2Cl2 showed that the methylidyne atoms originate from the dichloromethane solvent. ¹³CO-labeled 1 was prepared to 96% enrichment and revealed a resonance for the carbonyl ligands in the ¹³C-NMR spectrum at δ 207 with w1/2 = 940 Hz. Cluster 11b was found to desulfurize thiols and perform phosphinidene abstraction reactions via formation of the monomeric cluster Cp‘2Mo2Co2S4(η²,μ2-dppe) (18) or the oligomeric clusters [Cp‘2Mo2Co2S3(μ3-PPh)(η²,μ2-dppe)]n (19), respectively.

Allylic organolithiums generated by enantioselective deprotonation of N-Boc-N-(p-methoxyphenyl) allylic amines undergo conjugate additions with nitroalkenes to provide enecarbamates containing two contiguous stereogenic centers in good yields with high diastereoselectivities and enantioselectivities. Further elaboration of these adducts to enantioenriched substituted cyclopentanones and aminocyclopentanes is reported.