Synthesis and photophysical characterization of a titanium(IV) phthalocyanine-C60 supramolecular dyad

An axially substituted titanium(IV) phthalocyanine-fullerene donor-acceptor supramolecular dyad has been prepared by two different approaches, one of them representing a convenient convergent strategy. The dyad system exhibits photoinduced electron transfer upon irradiation with visible light to produce a microsecond lived charge separated state.     

Synthesis and photophysical characterization of a subphthalocyanine fused dimer-C60 dyad

Photophysical studies of a newly synthesized fused subphthalocyanine dimer-C60 revealed a complex cascade of energy transfer events to succeed the initial SubPc dimer photoexcitation.     

A convenient method for the synthesis of substituted thioureas

A convenient method for the synthesis of substituted thioureas by the reaction of primary amines with molybdenum dialkyl dithiocarbamates has been developed. Primary amines on reaction with 0.5 equiv of molybdenum xanthate produce the corresponding thioureas in moderate to good yields in short times. Similar reactions with propargylamine or 2-aminoethanol produce cyclic thiaoxazolidine and oxazolidine derivatives, respectively.     

A novel and convenient method for the synthesis of substituted naphthostyrils

3-Pyrrolyl-6-fluoro-naphthostyril 13 was synthesized via a base-catalyzed intramolecular cyclization of oxindole precursor 2 (Y=H). Derivatization of 2 (Y=I) through a one-pot reaction give 5-substituted naphthostyrils. This method allows convenient access to 3,5,6-trisubstituted naphthostyrils which may serve as a new template for CDK2 inhibition.     

Synthesis of a linear benzo[3]phenylene-[60]fullerene dyad

The synthesis of a new linear benzo[3]phenylene-[60]fullerene dyad 1 is achieved over 10 steps in 15% overall yield by using an efficient sequence combining a double cobalt(I)-mediated cyclotrimerization with a Bingel reaction.     

A convenient synthesis of a substituted phthalocyanine compound

A new substituted tetra-(4-octanethiol-5-nitro)phthalocyaninatocopper complex was synthesized by nucleophlic substitution of tetra-(4-bromo-5-nitro)phthalocyaninatocopper where the bromo activated by an ortho-nitro group is easily substituted by 1-octanethiol.     

Synthesis, cyclic voltammetry, and photophysical properties of a bridged o-phenylenediamine-C(60) dyad

The synthesis, complete spectroscopic characterization, cyclic voltammetry, and photophysical measurements of a new o-phenylenediamine-C(60) dyad are described. By using a tether strategy, only a single regioisomer was obtained. Cyclic voltammetry measurements indicate that the two electroactive groups do not interact in their singlet ground states. Photophysical investigations reveal a rapid photoinduced electron transfer between the singlet excited state of the fullerene acceptor and the o-phenylenediamine donor, yielding a charge-separated radical pair.     

N@C60-porphyrin: a dyad of two radical centers

Dyads of endohedral nitrogen fullerene and porphyrin have been synthesized. In the two-radical-center dyad, the copper(II) tetraphenylporphyrin suppressed the electron spin resonance (ESR) signal of N@C(60) through intramolecular dipolar coupling with a strength of 27.0 MHz. Demetalation of the metalloporphyrin moiety of the dyad, which effectively turned the two-radical-center dyad into a single-radical-center dyad, recovered 82% of the ESR signal of N@C(60). Such mechanism of switching a spin state on and off could find use in molecular spintronics applications.     

Synthesis, photophysical properties and in vitro photodynamic activity of axially substituted subphthalocyanines

A new series of subphthalocyanines substituted axially with an oligoethylene glycol chain [SPcB(OCH(2)CH(2))(n)OH, n = 3 (2) or 4 (3)] or a p-phenoxy oligoethylene glycol methyl ether chain [SPcBOC(6)H(4)(OCH(2)CH(2))(n)OCH(3), n = 2 (4) or 3 (5)] have been synthesised by substitution reactions of boron subphthalocyanine chloride SPcBCl (1) with the corresponding oligoethylene glycols, and characterised with various spectroscopic methods and elemental analysis. The molecular structure of one of these compounds (subphthalocyanine 4) has also been determined. As revealed by absorption spectroscopy, these compounds are essentially non-aggregated in DMF. The low aggregation tendency of these compounds results in a strong fluorescence emission and high efficiency to generate singlet oxygen. All these subphthalocyanines, being formulated with Cremophor EL, function as efficient photosensitisers and exhibit a high photocytotoxicity against HepG2 human hepatocarcinoma and HT29 human colon adenocarcinoma cells. The phenoxy analogues 4 and 5 show a relatively high photostability and are particularly potent towards these cell lines, with IC(50) values down to 0.02 microM.     

Solvent-polarity-tunable dimeric association of a fullerene (C60)-N,N-dimethylaminoazobenzene dyad: modulated electronic coupling of the azo chromophore with a substituted 3D fullerene

The tunable self-assembly of a fullerene (C(60))-N,N-dimethylaminoazobenzene (DPNME) molecular system as a function of solvent polarity in THF/water binary solvent is reported. Gradual increase of the volume fraction of the nonsolvent water in a 1×10(-5) M THF solution of DPNME at a mixed dielectric constant ε(mix)≈42 resulted in initial redshifting of the (1)(π→π(*)) absorption band, which signified the 1D head-to-tail or J-type arrangement of the DPNME molecular system. Further increase in the solvent polarity to ε(mix)≈66 evidenced formation of an antiparallel head-to-tail or H-type molecular arrangement in conjunction with the J-aggregates, thereby establishing a solvent-polarity-dependent dynamic equilibrium between the monomer ? J-aggregate ? H-aggregate. The controlled aggregation was governed by the synergetic effect of intermolecular donor-acceptor interaction between the electron-deficient fullerene ring and the electron-rich N,N-dimethylamino-substituted aromatic ring; typically, van der Waals and π-π interactions between the molecules constituting a pair of dimers were envisaged. An agreement between the semiempirically calculated drastically reduced oscillator strength of the DPNME H-dimer in the antiparallel configuration (0.69 vs. 1.29 in the monomeric DPNME) and the experimental electronic absorption spectra beyond ε(mix)=66 further strengthened this assignment to the hitherto forbidden antiparallel H-dimer. Complementing the above, the periodicity of molecular self-assembly dictated a monoclinic unit cell in the single-crystal XRD packing pattern with a C2/c space group; the molecules packed laterally with mutual interdigitation with the donor (E)-N,N-dimethyl-4-(p-tolyldiazenyl)aniline (AZNME) parts in an antiparallel fashion (contrary to the usual expectation for H-aggregates) with strong inter- and intrapair van der Waals and π-π interactions between the constituent fullerene moieties. Unlike those of porphyrin/phthalocyanine bowl-like donor-initiated architectures, a rare class of DPNME dyadic supramolecular self-assemblies was realized with π-extended 2D fullerene networks, in which the linear geometry of the AZNME donor and the conformational rigidity of the fullerene acceptor played crucial roles.     

Synthesis of C60-diphenylaminofluorene dyad with large 2PA cross-sections and efficient intramolecular two-photon energy transfer

The first, highly two-photon active C60 derivative comprised of a A-sp3-D conjugate structure was synthesized showing effective two-photon absorption cross-sections (sigma 2' = 196 x 10(-48) cm4 sec-1 molecule-1) in the nanosecond regime among the best values for diphenylaminofluorene-based AFX chromophores.     

Hydrogenolysis of the C-O bond of hydroxylactams as a convenient method for the synthesis of substituted isoindolin-1-ones

A simple and efficient method for the synthesis of isoindolin-1-ones containing alkyl or aryl substituents at positions 2 and (or) 3 was suggested. The method is based on the earlier unknown Pd⁰-catalyzed hydrogenolysis of hydroxylactams.     

A novel and convenient method to 4‐substituted coumarins

The palladium‐catalyzed cross‐coupling reaction of aryl‐; alkenyl‐; and cyclopropylboronic acids with 4‐trifluoromethanesulfonyloxycoumarin provides the corresponding 4‐substituted coumarins in yields of 63–85%. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:380–382, 2000     

A convenient method for the preparation of α-vinylfurans by phosphine-initiated reactions of various substituted enynes bearing a carbonyl group with aldehydes

α-Vinylfurans were obtained by phosphine-initiated cyclization of various enynes bearing a carbonyl group at the ene end in the presence of various aldehydes, in moderate to high yields. The reaction may consist of 1,6-addition of phosphine to the enynes, ring closure, and Wittig reaction between the ylid resulting from cyclization and an aldehyde. Thus, various aldehydes were able to be used in the reaction. The reaction was influenced greatly by the substituents at the acetylene position (R¹) and the α-position of the carbonyl group (R³).     

Synthesis and photophysical investigation of new porphyrin derivatives with beta-pyrrole ethynyl linkage and corresponding dyad with [60] fullerene

Two new beta-substituted arylethynyl meso-tetraphenylporphyrins, 2-[(4'-formyl)phenyl]ethynyl-5,10,15,20-tetraphenylporphyrin (system A) and 2-[(4'-methyl)phenyl]ethynyl-5,10,15,20-tetraphenylporphyrin (system B) and their zinc derivatives were synthesized by palladium catalysis, using a synthetic approach that affords high yields of the target systems. Comparative ultraviolet-visible (UV-vis), NMR, and cyclic voltammetry studies of such macrocycles reveal the presence of an extensive conjugation between the tetrapyrrolic ring and the linker, through pi-pi orbital interaction. This interaction was observed in the form of a "push-pull" effect that moves the electronic charge between the porphyrin and the aldehyde group of system A. System B, bearing a methyl group instead of the formyl group, was synthesized in order to evaluate the effect of the substitution on the charge delocalization, which is necessary to corroborate the push-pull mechanism hypothesis. The new porphyrin, system A, was also used as a starting material for the synthesis of new porphyrin-fullerene dyads in which the [60]fullerene is directly linked to the tetrapyrrolic rings by ethynylenephenylene subunits. Fluorescence and transient absorption measurements of the new dyads reveal that ultrafast energy and electron transfer occur, respectively, in nonpolar and polar solvents, with high values of the rate constant. The UV-vis, NMR, and cyclic voltammetry results show that it is possible for both energy and electron transfer between porphyrin and fullerene to take place through the pi-bond interaction. Such results evidence that the coupling between the donor and acceptor moieties is strong enough for possible photovoltaic applications.     

A convenient synthesis of substituted γ-pyrones

An efficient and general synthetic method for various 2-mono- and 2,6-disubstituted γ-pyrones has been developed. This utilizes the $\text{C}$-acylation (70–85%) of β-methoxy-α,β-enone lithium enolates $\text{4}$ by acid chlorides $\text{3}$ followed by the acid-catalyzed cyclization (>80%) of the resulting enols $\text{5}$ to γ-pyrones $\text{6}$.     

A convenient preparative method for anionic tris(substituted pyrazolyl)methane ligands

The synthesis of tris[3-(6-carboxypyridin-2-yl)pyrazol-1-yl]methane is described in a linear multi-step protocol. The pyridyl-pyrazolyl arms are first constructed before being condensed with chloroform. Careful study of the condensation reaction shows the presence of an isomeric form of the tris(pyrazolyl)methane derivative in which one of the pyrazolyl substituents is linked through the nitrogen atom at the 2 position of the pyrazol. After acid-catalysed isomerisation to the desired isomer, the intermediate compound was subjected to a carboalkoxylation reaction and a subsequent hydrolysis. These are some rare examples of reactions directly occurring on the tris(pyrazolyl)methane platforms.     

The crystal structure of octakispentoxy-phthalocyaninatocopper with pyridines axially substituted: the molecules stacked with J-aggregates

For coordination with two pyridines at the axis, the ring skeleton of octakispentoxyphthalo- cyaninatocopper maintains planar conformation, different from the structure of octakisbutoxy- phthalocyaninatocopper reported previously. The structure shows all molecules stacked along the b axis to form a one-dimensional molecular chain; neighboring molecules in the chain are arranged as J-aggregates, consistent with its crystal diffuse reflectance spectroscopy (DRS) having a red shift compared with its electronic absorption spectroscopy in pyridine.