Anthracenyl Ring Research Articles

New anthracene-based Cu(I) dithiocarbamates as AIEgens

The syntheses and structural characterizations of a series of anthracene-tethered Cu(I) phosphine dithiocarbamate complexes, [CuL(PPh3)2], are described in this article. All complexes were readily prepared from corresponding ligands with various acyclic and cyclic N-alkyl substituents and [Cu(PPh3)2(NO3)]. Steric hindrance imposed on the anthracenyl rings by dithiocarbamate, N-alkyl substituents and triphenylphosphine moieties in complexes 1-6 are not detected, as evidenced by the sharp aromatic resonances in 1H NMR spectra. X-ray crystallography reveals distorted tetrahedral chelation environments around the Cu(I) centers in 2 and 3 as well as extensive C–S···π and C–H···π intermolecular interactions in their solid state packings. The complexes display characteristic anthracene-based absorption and emission properties. The emission quantum yields of the complexes are poor (1.0–2.7 × 10−2) but the aggregation-induced emission effects are perceived in aqueous DMSO solutions. Especially, 6 with N-substituted cyclohexyl group displays the largest increase in emission intensity (ca. 7 times).

Synthesis and Studies of Di(p-Benzi)Decaphyrin and Di(9,10-Anthracenyl)Decaphyrin.

Two novel macrocycles, di(p-benzi)decaphyrin and di(9,10-anthracenyl)decaphyrin have been synthesized by condensing appropriate p-phenylene based pentapyrrane or 9,10-anthracenyl based pentapyrrane with pentafluorobenzaldehyde under acid catalyzed conditions. The pentapyrrane precursors were synthesized over sequence of steps starting with commercially available 1,4-dibromobenzene and 9,10-dibromoanthracene. The decaphyrin macrocycles were freely soluble in common organic solvents and characterized and studied by HR-MS, 1D and 2D NMR, absorption, cyclic voltammetry and computational techniques. The 1 H NMR spectra of both decaphyrins were almost similar with very few resonances, indicating their symmetrical nature in solution and the position of chemical shifts of various protons supports nonaromatic nature of decaphyrins. The DFT optimized structures revealed that both decaphyrins showed a doubly twisted figure of eight conformation and the p-phenylene rings in di(p-benzi)decaphyrin and anthracenyl rings in di(9,10-anthracenyl)decaphyrin did not participate in π-delocalization with rest of the respective decaphyrin macrocycle. Both decaphyrins showed sharp intense band in the region of 400-500 nm and a broad band in the region of 600-900 nm. The absorption bands of di(p-benzi)decaphyrin were significantly red shifted compared to di(9,10-anthracenyl)decaphyrin. The protonated derivatives of decaphyrins generated by addition of TFA to the toluene solution of decaphyrins showed distinct changes in colour and absorption spectral bands. The redox studies indicated that both decaphyrins are electron rich and undergo easier oxidations. The electrochemical and computational studies revealed that HOMO-LUMO energy gap was less in di(p-benzi)decaphyrin compared to di(9,10-anthracenyl)decaphyrin supporting the bathochromic shifts of absorption bands in di(p-benzi)decaphyrin. TD-DFT studies were in agreement with the experimental observations.

Exploring the syntheses, crystal structures and photophysical properties of new anthracene-tethered Ni(II) dithiocarbamates

A series of mononuclear anthracene-based dithiocarbamate Ni(II) complexes were readily prepared from one-pot reaction between corresponding secondary amine and nickel salt in the presence of carbon disulfide. X-ray crystallographic data reveals the marked difference in square planar structures of Ni(II) dithiocarbamate complexes with and without the presence of chloro and thiocyanato auxiliary ligands. Also, various intermolecular interactions of the complexes in the solid state such as π–π stackings, Ni···S linkages and CH···Ni anagostic bonds are detected. The 1H-NMR results evidently show the steric effect of the anthracenyl and dithiocarbamate moieties upon complexation. Importantly, phosphorus and proton magnetic resonance spectroscopies are tools to probe the facile transformation of the mixed-ligand complexes 3 into the congeners 1 in the solution. The absorption and emission spectral data describe the influence of anthracenyl rings on the photophysics of the complexes 1 and 2.

Heptadentate, Octadentate, Or Even Nonadentate? Denticity in the Unexpected Formation of an All-Carbon Donor-Atom Ligand in RhIII(Cp*)(Anthracenyl-NHC) Complexes.

Investigations on incorporating an N-flanking anthracenyl moiety to [Rh(Cp*)(NHC)Cl2] complexes surprisingly led to the formation of an intramolecular C-C bond between the Cp* and anthracenyl moieties, with additional auxiliary interactions between the metal and the anthracenyl ring system. In silico modeling supports a reaction mechanism whereby Rh(η4-tetramethylfulvene) intermediates undergo metallocycloaddition and the abstraction of a chlorido ligand, affording unique cationic complexes that feature Rh centers coordinated by a nonadentate ligand with exclusively carbon donor atoms. Some Rh-C interactions were extremely weak but nevertheless exhibited covalent bonding character. These weak Rh-C interactions were readily displaced by stronger electron donors, and the nonadentate ligand reverted to the heptadentate coordination mode observed in the intermediate. As far as we are aware, this study provides the first conclusive evidence of complexes bearing a single nonadentate κ9-coordinating ligand that features only carbon donors bound to a metal center.

Characterization of platinum(II) complexes exhibiting inhibitory activity against the 20S proteasome.

Proteasome inhibitors are useful for biochemical research and clinical treatment. In our previous study, we reported that the 4N-coordinated platinum complexes with anthracenyl ring and heterocycle exhibited proteasome-inhibitory activity. In the present study, the structure–activity relationships and characterization of these complexes were determined for the elucidation of the role of aromatic ligands. Lineweaver–Burk analysis revealed that the chemical structure of heterocycles affects the binding mode of platinum complexes. Platinum complexes with anthracenyl ring and pyridine showed competitive inhibition, although platinum complexes with anthracenyl ring and phenanthroline showed non-competitive inhibition. The structure–activity relationships demonstrated that anthracenyl moiety plays a crucial role in proteasome-inhibitory activity. The platinum complexes with naphthyl or phenyl rings exhibited lower inhibitory activities than the platinum complex with anthracenyl ring. The reactivity with N-acetylcysteine varied according to the chemical structure of complexes.

Anthracene-based Ni(II) thiosemicarbazones with novel intramolecular π–π stackings

Four new Ni(II) complexes were obtained from the reaction between anthracene-based thiosemicarbazones and inorganic metal salt. Structural investigation of the complexes using X-ray crystallography reveals unusual cis geometries driven by intramolecular π–π stackings between anthracenyl rings. Due to the novel interactions, the anthracenyl protons H1,8,2,7 are not observed and the imine proton is largely shifted in 1H NMR spectra. The UV–Vis and photoluminescent data clearly indicate strong perturbation of intramolecular π–π stackings on electronic structure of anthracenyl cores, namely broadening of absorption and emission bands.

A highly selective fluorescent anthracene-based chemosensor for imaging Zn2+ in living cells and zebrafish

A new fluorescent chemosensor (An3) bearing anthracenyl rings was designed and developed for detection of Zn2+. Addition of Zn2+ into An3 gave rise to a fluorescent turn-on response at 424 nm whereas Al3+, Cd2+, Co2+, Cu2+, K+, Mg2+, Zn2+, Ca2+, Fe3+, Mn2+, Ni2+, Pb2+, and Hg2+ did not induce any emission intensity enhancement. Furthermore, the probe exhibited high selectivity toward Zn2+ and a very low detection limit (36 nM) based on chelation-enhanced fluorescence. Theoretical calculations revealed the possible formation of 1:1 and 1:2 complexes between An3 and Zn2+. In bioimaging experiments, the chemosensor displayed low cytotoxicity and good biocompatibility, rendering it an effective tool for fluorescent visualization of Zn2+ in living cells and zebrafish models.

Synthesis, Characterization, Antibacterial, Antifungal and Cytotoxic Activity of Curcuminoid Analogues with Trisubstituted Phenyl and Anthracenyl ring and their Zinc (II), Copper (II) and Vanadyl (IV) Chelates

Two curcuminoid analogues 1,7-Bis(3,4,5-trimethoxy phenyl)-1,6-heptadiene-3,5-dione;1,7-di(9-anthracenyl)-1,6-heptadiene3,5dione, were synthesized and characterized by UV, IR, 1 H NMR, 13 C NMR and mass spectral techniques. The Zn (II), Cu (II), VO (IV) complexes of the two curcuminiod analogues were synthesized and characterized. Antibacterial, Antifungal and cytotoxic activity of the curcuminoid analogues and their transition metal chelates were studied. The metal chelates were found to be more active than curcuminoid analogues in antibacterial and antifungal activities. Curcuminod analogue-Metal complexes exhibited more cytotoxicity in cancer cell lines than the curcuminoid analogues. Among the metal chelates, the Cu (II) chelate of 1,7-di(9-anthracenyl)-1,6-heptadiene3,5dione compound was found to be very active against cancer causing cells. VO(IV)complex of 1,7-di(9-anthracenyl)-1,6-heptadiene3,5dione showed enhanced antifungal activity and Cu(II) complex of 1,7-di(9-anthracenyl)-1,6-heptadiene3,5dione was most effective against bacterial strains.

Synthesis, spectroscopy, electrochemistry, and coordination chemistry of substituted phosphine sulfides and selenides

Phosphines and phosphine chalcogenides are important ligands for various metal systems, especially catalysts. Based on previously synthesized phosphine oxide ligands, we describe here the synthesis and characterization of a series of compounds having the general formula, EPPh2Ar, E=S, Se; Ar=1-naphthyl, 9-phenanthryl, 9-anthracenyl, 1-pyrenyl. Reaction of EPPh2(9-phenanthryl), E=S, Se, with HAuCl4 yields ArPh2PEAuCl. Similar to the phosphine oxide derivative, the anthracenyl compounds, EPPh2(9-anthracenyl), showed a nonplanar conformation within the anthracene ring as observed using X-ray crystallography. The difference in fluorescence spectrum relative to the parent aryl species is attributed to this deformation. The deviation is probably due to steric strain within the phosphine ligand due to its position on the anthracenyl ring since DFT calculations suggest that the 1-anthracenyl ligand should be planar. Each compound has been characterized using 1H, 13C, 31P, and (where applicable) 77Se NMR, and IR spectroscopy, with structure determination by X-ray crystallography. Finally, the electrochemistry of the unoxidized phosphines is reported, showing one-electron reductions in the polycyclic aromatic hydrocarbons.

A non-planar crystal polymorph of 1,2-bis(9-anthracenyl)ethyne

1,2-Bis(9-anthracenyl)ethyne was synthesized and a new crystal polymorph was discovered. The previously reported structure was completely planar with a torsional angle between the two anthracenyl rings of 0.0°, whereas the new polymorph had a torsional angle of 66.6°. The new polymorph also stacks differently between molecules and has greater π–electron overlap. In solution, the spectroscopic characteristics of both polymorphs were identical, but in the solid-state, results of red-shifted spectra for the co-planar polymorph indicate a strikingly simple example of the effect on UV–vis and fluorescence spectra of extending π-conjugation wrapped up in one molecule with two polymorphs. It was also determined that the co-planar polymorph is favored with rapid crystallization, whereas the twisted polymorph prefers slow crystallization. This may indicate that the co-planar polymorph is kinetically favored and the twisted polymorph is thermodynamically favored.

Divergent Approach to the Bisanthraquinone Natural Products: Total Synthesis of (S)-Bisoranjidiol and Derivatives from Binaphtho-para-quinones

The development of the first asymmetric synthesis of a chiral anthraquinone dimer is outlined, resulting in the first total synthesis of (S)-bisoranjidiol. Rather than a biomimetic dimerization retrosynthetic disconnection, the anthracenyl ring systems are generated after formation of the axially chiral binaphthalene framework. This synthetic strategy has enabled the synthesis of several analogues. Key features of the synthesis include the enantioselective coupling of a hindered 2-naphthol containing substitution peri to the site of C-C bond formation, the regioselective oxidation of 8,8'-hydroxylated binaphthols to binaphtho-para-quinones, and a tandem regioselective Diels-Alder/aromatization reaction.

Dithia[3.3]paracyclophane-bridged bimetallic ruthenium acetylide complexes: synthesis, structures and influence of transannular π–π interactions on their electronic properties

Two dithia[3.3]paracyclophane-bridged bimetallic ruthenium acetylide complexes 2 and 3, in which the upper deck of the cyclophanes were assembled with naphthalenyl and anthracenyl rings, have been designed and synthesized. X-ray crystal structures of 2 and 3 show that there are effective transannular π–π interactions between the two rings in the cyclophane unit. Electrochemistry studies revealed that the successive introduction of naphthalenyl and anthracenyl rings reduced the thermodynamic stability of the corresponding mixed-valence states of 2 and 3. Radical cations and dications of complexes 2 and 3 were generated after the addition of 1.0 or 2.0 equivalents of ferrocenium hexafluorophosphate ([FcH][PF6]). The ν(C≡C) of radicals 2+ and 3+ shift 86 nm and 88 nm in contrast to 2 and 3, respectively. UV-Vis-NIR spectra of 2+ and 3+ exhibited three enveloped transitions in the NIR (10,000–4000 cm(−1)) range. DFT studies showed that the compositions of the FMOs of 2 and 3 are more naphthalenyl and anthracenyl in character than the upper deck of complex 1. Spectroscopy and DFT studies indicated that the influence of transannular π–π interactions on the electronic transitions is more pronounced than in complex 1.

1,3-Diallyl-1H-anthra[1,2-d]imidazole-2,6,11(3H)-trione

In the title compound, C21H16N2O3, the fused-ring system (r.m.s. deviation = 0.067 Å) is slightly buckled at the carbonyl C atom of the anthracenyl ring system [deviation = 0.177 (1) Å] that is closer to an allyl substituent. The two allyl units lie on the same side of the fused-ring plane but are oriented in opposite directions, with N—C—C—C torsion angles of 126.9 (2) and 116.7 (2)°. In the crystal, the mol­ecules are linked into chains propagating along the b axis by C—H⋯O hydrogen bonds.

Photooxidation of a Platinum-Anthracene Pincer Complex: Formation and Structures of PtII-Anthrone and -Ketal Complexes

Irradiating the cyclometalated pincer complex Pt(II)(DPA)Cl (1, DPA = 1,8-bis(diphenylphosphino)anthracene) in the presence of O(2) led to three sequential oxidations of the anthracenyl ring. The first photoproduct, a Pt(II)-9,10-endoperoxide complex, was converted photochemically to a Pt(II)-9-hydroxyanthrone complex A which was further oxygenated to a Pt(II)-hemiketal (B). The oxidation of A, which could be accelerated by light irradiation, probably involved a Pt(II)-anthraquinone intermediate. B underwent acid-catalyzed ketalization to form a binuclear Pt(II)(2)-diketal (B1). The photolysis was followed by UV-vis absorption and NMR spectroscopy, and the structures of A and B1 were characterized by single crystal X-ray diffraction.

Regioselective Double Cycloplatination of 9,10-Bis(diphenylphosphino)anthracene

Double cyclometalation of 9,10-bis(diphenylphosphino)anthracene (PAnP) by Pt(L)(OTf)2 (L = diphosphines, OTf = CF3SO3) gives rise to the geometrical isomers syn- and anti-[Pt2(L)2(PAnP-H2)](OTf)2 (Pt2). The reaction is regioselective, with the syn-isomer being the kinetic product. The cyclomelation is reversible, and thermodynamic product distribution is obtained after prolonged standing. The ratio of the isomers is subject to the influence of solvents and ancillary diphosphines. Protonolysis of the Pt−C leads to a monocyclometalated intermediate. A mechanistic postulate that invokes a preferential electrophilic attack of the Pt ions at the C−H bonds of the anthracenyl ring is proposed to explain the regioselectivity.

Synthesis and Electronic Spectroscopy of Luminescent Cyclometalated Platinum−Anthracenyl Complexes

Dicyclometalated complexes syn- and anti-[Pt2(L)2(PAnP-H2)](OTf)2 (Pt2) are synthesized from reactions of 9,10-bis(diphenylphosphino)anthracene (PAnP) and Pt(L)(OTf)2 (L = diphosphines, OTf = CF3SO3). Because of metal perturbation on the electronic structure of the anthracenyl ring, the 1B2u− ← 1Ag transition, which is forbidden in anthracene, is observed in the electronic spectra of Pt2. The complexes display fluorescence arising from the ligand-centered S1 excited state. No significant heavy atom effect is observed in the Pt2 complexes. To understand the effect of the number of Pt ions on the extent of perturbation, a mononuclear analogue, [Pt(dppe)(PAn-H)]ClO4 (PAn = 9-diphenylphosphinoanthracene), is prepared and its spectroscopy studied.

Synthesis, Structure and Spectroscopic Properties of Novel9,10‐Bis{[6‐(diphenylphosphanyl)‐2‐pyridylmethyl]propylaminomethyl}anthracene‐Bridged Group 11 Metal (M = Cu I and Ag I ) Dinuclear Complexes

Dinuclear complexes [M2(μ-BPNNAn)]X2 (M = CuI, X = ClO4–1, X = BF4–2; M = AgI, X = BF4–3, X = ClO4–4) have been prepared by treating 9,10-bis{[6-(diphenylphosphanyl)-2-pyridylmethyl]propylaminomethyl}anthracene (BPNNAn) with M(CH3CN)4X in CH2Cl2. The structures of complexes 1, 2 and 3 have been determined by single-crystal X-ray diffraction studies. In the complexes, BPNNAn acts as a chelating ligand and two metal ions riding on two bridgehead carbon atoms in the anthracene group leads to the deformation of the anthracenyl ring. The Cu–Arene charge transfer interaction is observed from the nonfluorescent emission of Cu complex 1, while the Ag complex 3 exhibits dual emission at high concentrations in a CH2Cl2 solution. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Synthesis, Characterization and Crystal Structures of New Ruthenium Carbonyl Clusters Derived from (9-Anthracenyl)diphenylphosphine*

Thermal reaction of [Ru2(CO)6(μ-PFu2)(μ-η1,η2-Fu)] (Fu=2-furyl) with (9-anthracenyl)diphenylphosphine (AnPPh2) produces a novel diruthenium complex [Ru2(CO)5(μ-PFu2)(μ-η1,η1,η2-C14H8PPh2)] (1) in good yield whereas the corresponding reaction between [(μ-H)4Ru4(CO)12] and AnPPh2 gives [HRu(CO)3(PPh2C14H8)][(μ-H)4Ru4(CO)11(AnPPh2)] (2). Both compounds 1 and 2 were fully characterized by spectroscopic methods and their X-ray crystal structures were determined. For 1, initial coordination of the PPh2 functionality at the Ru atom is accompanied by cyclometalation of the anthracenyl ring to form a Ru–C σ bond together with concomitant formation of a π bond to the adjacent Ru center and loss of the furyl ligand. The formation of 2 involves the cleavage of two Ru–Ru bonds, and the making of a Ru–P bond, followed by orthometalation of the anthracenyl ring. The optical absorption and emission spectra of 1 were recorded and the results were correlated to the DFT calculations.

Design of New Modifiers for the Enantioselective Hydrogenation of Ethyl Pyruvate

All efficient chiral modifiers for Pt in the enantioselective hydrogenation of α-ketoesters possess a basic, secondary or tertiary N atom for interacting with the carbonyl group of the reactant and an aromatic ring system for adsorptive anchoring of the activated complex on Pt. Analysis of the available data suggested that an enlargement of the naphthalene or quinoline anchoring moiety should improve the enantioselection. Accordingly, 1-(9-anthracenyl)-2- (1-pyrrolidinyl)ethanol (10) has been synthesized and tested in the hydrogenation of ethyl pyruvate. The best enantiomeric excess achieved with the new modifier was 87%, which is 12% higher than the optimized value obtained with the corresponding naphthalene derivative (4). A further advantage of the new modifier is the higher stability against self-hydrogenation. Hydrogenation of ethyl pyruvate in the presence of modifier mixtures indicated the following order of adsorption strength on Pt: cinchonidine>10>4. This ranking correlates with the best enantiomeric excesses obtained with these modifiers. Compared with the other modifiers, the number of possible conformations for 10 is reduced because of the symmetry of the anthracenyl ring system. Molecular mechanics calculations suggest that the energy and geometry of the transition complexes between ethyl pyruvate and 10 or 4 are similar. Accordingly, the better efficiency of 10 should be due to its stronger adsorption on Pt and higher acceleration of the modified reaction compared with the competing nonenantioselective (unmodified) reaction. Substituting the 9-anthracenyl group of 10 with a 9-triptycenyl moiety led to a complete loss of enantiodifferentiation, demonstrating that the extendedflataromatic ring system is a crucial structural element of efficient modifiers for α-ketoester hydrogenation.

Ferrocenyl anthracenes: Synthesis and molecular structure

The synthesis of a series of ferrocenylanthracene derivatives is described, utilising the palladium catalysed coupling reaction of 1,1′-bis(chlorozincio)ferrocene with halo-anthracenes. Bis-1,1′-(9-anthracenyl)ferrocene ( 1) was characterised by single crystal X-ray diffraction and shows an eclipsed ferrocenyl geometry. X-ray crystallographic studies indicate that there are no clear stacking interactions of either an intra- or intermolecular nature between the anthracenyl rings in the structure. A series of 9- and 10-disubstituted ferrocenylanthracene derivatives has also been prepared. In each case the palladium catalyst (Pd(dppf)Cl 2) is recovered in a modified form, e.g. as the [(dppf)PdBr(9-anthracenyl)] complex in the synthesis of bis-1,1′-(9-anthracenyl)ferrocene. The single crystal X-ray structure of one such palladium complex [(dppf)PdBr-9-(10-chloroanthracenyl)] ( 15a) has been determined in a case where chloride/bromide exchange had occurred in the palladium complex intermediate. The potential application of compound 1 as synthon for the construction of a molecular sensing device is discussed. Cyclic voltammetry and fluorescence studies have been carried out for selected derivatives.