Carbazole N-substituent effect upon DTMA: stabilizing and photochromic modulating

Dithienylmaleimide derivatives 7–27 were synthesized by introducing N-substituted carbazole for photo-stabilizing purpose, and the structures were fully confirmed. The photochromism and photo-stability were recorded via UV–vis spectra. Only ortho compounds 8–17 with N-substituents on carbazole moiety showed escalated photochromic change, while compound 7 and the para counterparts 18–27 showed no appreciable photochromism. Additionally, compounds 8–18 exhibited good photo-stability except 17 under 254 nm irradiation. The unstability of 17 may probably due to overrunning hindrance. These photochromic patterns indicated that hindrance and electronic effect mutually paid a decisive influence on the photochromism and photo-stability, which potentially exploited a new way to construct novel photochromic materials with regulable and conceivable performance.     

Separation and identification of three epimeric pairs of new C-glucosyl anthrones from Rumex dentatus by on-line high performance liquid chromatography–circular dichroism analysis

Six C-glucosyl anthrones were characterized as three pairs of epimers by on-line high performance liquid chromatography–circular dichroism (HPLC–CD) analysis and isolated from the roots of Rumex dentatus by column chromatography. Their structures were elucidated by mass spectrometry, nuclear magnetic spectroscopy and HPLC–CD analysis. They are 10R-C-β-d-glucosyl-10-hydroxyemodin-9-anthrone (rumejaposide E, 1) and 10S-C-β-d-glucosyl-10-hydroxyemodin-9-anthrone (rumejaposide F, 2), 10R-C-β-d-glucosylemodin-9-anthrone (rumejaposide G, 3) and 10S-C-β-d-glucosylemodin-9-anthrone (rumejaposide H, 4), 10S-C-β-d-glucosyl-10-hydroxychrysophanol-9-anthrone (cassialoin, 5) and 10R-C-β-d-glucosyl-10-hydroxychrysophanol-9-anthrone (rumejaposide I, 6). Rumejaposides F–I (2–4 and 6) were new C-glucosyl anthrones. Rumejaposide E (1) and cassialoin (5) were isolated for the first time in Rumex plants. On-line HPLC–UV–CD analysis was a useful tool for structure elucidating epimeric C-glycosides anthrones 3–6 because of the poor stability of the pure isomers (3 and 4) and the minute quantity of 5 and 6 in the mixture.     

Nortriterpenoids from Schisandra chinensis and their absolute configurational assignments by electronic circular dichroism study

Twelve new nortriterpenoids, namely wuweizidilactones J–P (1–7), schindilactones I–K (8–10), preschisanartanin N (11), and schisdilactone J (12), as well as 23 known analogues, were isolated from the leaves and stems of Schisandra chinensis. The absolute configurations of 1 and 11 were established by calculated electronic circular dichroism (ECD) spectra and that of 7 was confirmed by single-crystal X-ray diffraction. The absolute configurations of 2–6, 8, and 9 were determined by an empirical comparison of their experimental ECD spectra with that of 1. It is the first time that the ECD spectra of 18(13→14)-abeo-schiartane-, 18-norschiartane-, and schisanartane-type nortriterpenoids possessing an α,β-unsaturated-γ-lactone moiety are presented, this method providing an alternative means of obtaining absolute configurational assignments for these types of nortriterpenoids. All isolates were evaluated for their anti-acetylcholinesterase and anti-butyrylcholinesterase activities, and compounds 8, 13, 23, and 31 show anti-acetylcholinesterase activity at concentrations of 50 μM, with 12.7, 10.7, 16.6, and 32.1% inhibition, respectively.     

Dimolybdenum complexes containing anions of N,N′-bis(pyrimidine-2-yl)formamidine and N-(2-pyrimidinyl)formamide

The reactions of Mo₂(O₂CCH₃)₄ with different equivalents of N,N′-bis(pyrimidine-2-yl)formamidine (HL1) and N-(2-pyrimidinyl)formamide (HL2) afforded dimolybdenum complexes of the types Mo₂(O₂CCH₃)(L1)₂(L2) (1) trans-Mo₂(L1)₂(L2)₂ (2) cis-Mo₂(L1)₂(L2)₂ (3) and Mo₂(L2)₄ (4). Their UV–Vis and NMR spectra have been recorded and their structures determined by X-ray crystallography. Complexes 2 and 3 establish the first pair of trans and cis forms of dimolybdenum complexes containing formamidinate ligands. The L1 ligands in 1–3 are bridged to the metal centers through two central amine nitrogen atoms, while the L2 ligands in 1–4 are bridged to the metal centers via one pyrimidyl nitrogen atom and the amine nitrogen atom. The Mo–Mo distances of complexes 1 [2.0951(17) Å], 2 [2.103(1) Å] and 3 [2.1017(3) Å], which contain both Mo?N and Mo?O axial interactions, are slightly longer than those of complex 4 [2.0826(12)–2.0866(10) Å] which has only Mo?O interactions.     

Half-sandwich η-arene–ruthenium(II) complexes bearing 1-alkyl(benzyl)-imidazo[4,5-f][1,10]-phenanthroline (IP) derivatives: the effect of alkyl chain length of ligands to catalytic activity

The reaction of bromoalkanes (R–Br; (3), R=C_nH_2n+1, n=4 (a), 8 (b), 12 (c),18 (d)) and bromobenzyl derivatives (R′–Br; (4), R′=CH₂C₆H₂(CH₃)₃-2,4,6 (a); CH₂C₆H(CH₃)₄-2,3,5,6 (b); CH₂C₆(CH₃)₅ (c)) with 1H-imidazo[4,5-f][1,10]-phenanthroline (IP)(L₂) gave the corresponding 1-R-imidazo[4,5-f][1,10]-phenanthroline (IPR)(L_3a–d) and 1-R′-imidazo[4,5-f][1,10]-phenanthroline(IPR')(L_4a–c) ligands, respectively. Treatment of L_3a–d and L_4a–d with [Ru(p-cymene)Cl₂]₂ led to the formation of [Ru(p-cymene)(IPR)Cl]Cl (RuL_3a–d) and [Ru(p-cymene)(IPR′)Cl]Cl (RuL_4a–c). New ruthenium(II) complexes RuL_3a–d and RuL_4a–c were characterized by elemental analysis, FTIR, UV–visible and NMR spectroscopy. In order to understand effects of these changes on the N-substituent of imidazol on IP and how they translate to catalytic activity, these new RuL₂, RuL_3a–d and RuL_4a–c were applied in the transfer hydrogenation of ketones by 2-propanol in presence of potassium hydroxide. The activities of the catalysts were monitored by NMR and GC analysis.     

Synthesis and characterization of 2H-pyrano[3,2-c]coumarin derivatives and their photochromic and redox properties

A series of 2H-pyrano[3,2-c]chromen-5-one derivatives were synthesized and characterized. Their photochromic and redox properties were investigated by the UV-vis absorption spectroscopy. While compounds with one or two phenyl groups incorporated at the 2-position were present in both ring-opened (5a and 10a) and ring-closed (6a and 11a) forms, the incorporation of an N,N-dimethylamino group on either side of the aromatic ring resulted in formation of the ring-opened (5b and 10b) forms only. The ring-closed forms 13 and 18 with a methyl substituent at the 3-position of the pyran moiety failed to exhibit photochromic behavior. Compound 23 with an N,N-dimethylamino group on the aromatic ring displayed increasing shoulder absorption in the visible region and a distinct change of color upon UV irradiation. The non-fluorescent 10b instantly changed from dark red to colorless, when treated with sodium borohydride. The reduced 28 was blue fluorescent with a quantum yield of 0.46 and could be returned to its original color via DDQ oxidation.     

Novel phthalocyanines bearing four 4-phenyloxyacetic acid functionalities

Metal-free (2) and Co(II), Zn(II), Ni(II), Cu(II) metallophthalocyanines (2a–d) with four 4-phenyloxyacetic acid groups on the periphery were prepared by cyclotetramerization of new p-(3,4-dicyanophenoxy)phenylacetic acid (1) and the corresponding divalent metal salts. Further reactions of these products with thionylchloride and then benzylamine in tetrahydrofuran, and octanol in pyridine gave amide (3, 3a–d) and ester (4, 4a–d) derivatives, respectively. The new compounds have been characterized by elemental analyses, IR, UV–Vis, mass and ¹H NMR spectroscopy. The redox properties of compounds 2 and 2a–d were identified by cyclic voltammetry.     

Salen-type nickel(II), palladium(II) and copper(II) complexes having chiral and racemic camphoric diamine components

Chiral and racemic Salen-type Schiff-base ligands (H₂L¹, H₂L² and H₂L³), condensed between D-(+)- and D,L-camphoric diamine (also known as (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diamine) and 2-hydroxybenzaldehyde or 3,5-dibromo-2-hydroxybenzaldehyde with a 1:2 molar ratio, have been synthesized and characterized. A series of new nickel(II), palladium(II) and copper(II) complexes of these chiral and racemic ligands exhibiting different coordination number (4, 5 and 6) have been characterized with the formulae [NiL¹]·CH₃OH (3), [NiL¹]·H₂O (4), [NiL²] (5), [PdL²] (6), [Cu₂(L²)₂(H₂O)] (7) and [NiL³(DMF)(H₂O)] (8). Different solvent molecules in 3 and 4 (methanol and water molecules) as well as different apical ligands in 7 and 8 (water and DMF molecules) are involved in different O–H···O hydrogen bonding interactions to further stabilize the structures. UV–Vis (UV–Vis), circular dichroism (CD) spectra and thermogravimetric (TG) analyses for the metal complexes have also been carried out.     

Dihydroanthracenone metabolites from the endophytic fungus Diaporthe melonis isolated from Annona squamosa

Chemical investigation of the endophytic fungus Diaporthe melonis, isolated from Annona squamosa, yielded two new dihydroanthracenone atropodiastereomers, diaporthemins A (1) and B (2), together with the known flavomannin-6,6′-di-O-methyl ether (3). The structures of the new compounds were established on the basis of extensive 1D and 2D NMR spectroscopy, as well as by high resolution mass spectrometry and by CD spectroscopy. Compounds 1–3 were tested for their antimicrobial activity against a multi-resistant clinical isolate of Staphylococcus aureus 25697, a susceptible reference strain of S. aureus ATCC 29213 and against Streptococcus pneumoniae ATCC 49619. Compound 3 strongly inhibited S. pneumonia growth with a MIC value of 2 μg/mL, and showed moderate activity against the S. aureus multi-resistant clinical isolate and susceptible reference strain (MIC 32 μg/mL), whereas 1 and 2 were not active against the tested strains.     

Unexpected formation of new photochromic compounds derived from 3,3-diphenyl-3H-naphtho[2,1-b]pyran-1-one

Two new unexpected photochromic compounds were obtained from naphtho[2,1-b]pyran-1-one 1. The reaction of this ketone with the silyl enol ether methyl trimethylsilyl dimethylketene acetal, catalyzed by TiCl₄, afforded the photochromic dihydronaphtho[2,1-b]pyranone 2. The Reformatsky reaction of ketone 1 with ethyl bromoacetate led to the formation of the expected alcohol that under acid treatment gave, unexpectedly, the novel photochromic benzocoumarin 6. UV irradiation compounds 2 and 6 in solution provided thermally stable photoproducts that returned to the initial uncoloured forms under visible irradiation. The photochromic behaviour of these compounds and the structures of the photoproducts formed in these reactions were characterized by 1D and 2D NMR.     

Ion-pair charge transfer complexes with intense near IR absorption: Syntheses,crystal structures,electronic spectra and DFT calculations

Five ion-pair complexes, consisting of R-benzylidene-1-aminopyridinium derivatives and [Ni(mnt)₂]²⁻ (R = p-nitro (1), p-methyl (2), p-bromo (3), p-chloro (4) and m-nitro (5); mnt²⁻ = maleonitriledithiolate), were synthesized and structurally characterized. As for 1, it is interesting to observe a large deviation from square-planar coordination geometry for the Ni atom, while no deviation is observed in the other four complexes. In the solid state, UV–Vis–NIR spectra of 2–5 show similar properties with intense absorption in the 200–750 nm and moderate near IR absorption in the 750–1000 nm region, whereas 1 exhibits an intense absorption from UV/Visible to near-IR region (200–1100 nm). This unique spectral feature of 1 is attributed to its distinctive structural differences from 2 to 5, namely the strong intermolecular packing interactions between anions and cations, as well as a significant deviation from the planarity of the anion. Based on DFT and TDDFT calculations, near-IR absorbance bands in 1–5 were assigned to combined transitions of d–d, MLCT and π–π^∗ in the [Ni(mnt)₂]²⁻ anion as well as the ion-pair charge transfer (IPCT) from the anionic HOMO to the cationic LUMO. The IPCT band position in acetonitrile is independent of the substituent group feature in benzene ring of cations for 1–5, which could be interpreted that the substituent group in benzene ring only has a minor contribution to the cationic LUMO.     

Three-step pathway towards bis(1,2,3-triazolyl-γ-propylsilatranes) as Cu fluorescent sensor,via ‘Click Silylation’

A series of substituted aniline derivatized bis(1,2,3-triazolyl-γ-propylsilatranes) 3a–3f were designed in good yield from their triethoxysilane analogues via Cu(I) ‘Click Silylation’. All the silatranes 3a–3f were characterized by IR, NMR (¹H, ¹³C) and HRMS studies. All these compounds were explored for their thermal stability by thermogravimetric analysis (TGA)/differential thermal analysis (DTA)/differential scanning calorimetry (DSC) study and electronic properties by UV–vis spectroscopy and fluorescence study. The binding of silatranes 3a–3f to Cu²⁺ ion proves them to be good chemosensor. These silatranes were subjected to time dependent hydrolysis under normal atmospheric conditions. IR spectroscopic data support hydrolytic instability of 3a, 3c and 3e.     

Synthesis,characterization and metal ion complexation and extraction capabilities of calix[4]arene Schiff base compounds

The syntheses, characterization and metal ion complexation and extraction capabilities of six new calix[4]arene Schiff base compounds, 5–10, are reported. The preparation of the compounds was achieved by the condensation of 5,17-diamino-11,23-di-tert-butyl-25,27-di-n-butoxy-26,28-dihydroxycalix[4]arene with the appropriate aldehyde (5-bromosalicylaldehyde for 5, 4-anisaldehyde for 6, 4-(dimethylamino)benzaldehyde for 7, 9-anthracenecarboxaldehyde for 8, 1-pyrenecarboxaldehyde for 9, and 9-fluorenecarboxaldehyde for 10) in refluxing ethanol. The compounds were characterized by ¹H and ¹³C NMR spectroscopy, IR spectroscopy, high-resolution mass spectrometry and elemental analysis. The X-ray crystal structures of 7, 8 and 9 (as dichloromethane solvates) revealed that the calixarene molecules adopt H-bond stabilized, distorted-cone conformations and form centrosymmetric dimers in the solid state. Compounds 5–10 did not form host–guest complexes with NEt₄[(bdt)MoO₂(OSiPh₃)] (bdt^2–=benzene-1,2-dithiolate), a potential precursor for biologically relevant oxosulfido-Mo(VI/V) enzyme models; such host–guest complexes have the potential to stabilize these sought-after but highly reactive model compounds. In addition, the capabilities of 5–10 to extract selected metal ions (Ni²⁺, Co²⁺, Cu²⁺, Zn²⁺, Ag⁺, Pb²⁺, Cd²⁺ and Hg²⁺) from an aqueous into an organic phase have been assessed by picrate extraction experiments. Compound 5 displayed exceptional selectivity towards Ni²⁺, compound 7 exhibited enhanced extraction towards all of the metal ions tested and compounds 6, 9 and 10 showed very high selectivity towards Hg²⁺. On the other hand, compound 8 exhibited negligible capacity to extract any of the metal ions tested.     

Hypervalent and binuclear silicon and germanium derivatives from bis-(3,5-di-tert-butyl-2-phenol)-oxamide

The reactions of bis-(3,5-di-tert-butyl-2-phenol)oxamide (1) with Cl₂SiR₂ (Me or Ph) or Cl₂GeR₂ (Me, nBu or Ph) in THF provided binuclear pentacoordinated silicon and germanium compounds: bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-dimethylsilane (2), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-diphenylsilane (3), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-dimethylgermane (4), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-di-n-butylgermane (5) and bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-diphenylgermane (6). The mono-nuclear tetracoordinated silicon compounds N-acetyl-bis-(3,5-di-tert-butyl-2-oxo-phenyl)-amide-bis-(dimethylsilane) (8) and N-acetyl-bis-(3,5-di-tert-butyl-2-oxo-phenyl)-amide-bis-(diphenylsilane) (9) were synthesized from N-(3,5-di-tert-butyl-2-phenol)acetamide (7) and Cl₂SiR₂ (R = Me and Ph). Comparison of the ²⁹Si NMR chemical shifts of the penta- (2 and 3) and tetracoordinated (8 and 9) silicon compounds provided information about the intramolecular coordination of the carbonyl group to the silicon atom. Compounds 3 and 6 were characterized by single-crystal X-ray analyses. They have planar hexacyclic structures where the central atoms present distorted tbp geometries with one nitrogen and two carbon atoms in equatorial positions and two oxygen atoms in apical positions.     

Synthesis,characterization and electrochemical properties of novel metal free and zinc(II) phthalocyanines of ball and clamshell types

The phthalodinitrile derivative 1 was prepared by the reaction of 4-nitrophthalonitrile and 1,3-dimethoxy-4-tert-butylcalix[4]arene in dry dimethylsulfoxide as the solvent, in the presence of the base K₂CO₃, by nucleophilic substitution of an activated nitro group in an aromatic ring. The tetramerization of compound 1 gave a binuclear zinc(II) phthalocyanine and a metal-free phthalocyanine of the ball type, 2 and 3, respectively. Its condensation with 4,5-bis(hexylthio)phthalonitrile results in a binuclear phthalocyanine of the clamshell type, 4. The newly synthesized compounds were characterized by elemental analysis, UV–Vis, IR, MS and ¹H NMR spectra. The electronic spectra exhibit an intense π → π^∗ transition with characteristic Q and B bands of the phthalocyanine core. The electrochemical properties of 2–4 were examined by cyclic voltammetry in non-aqueous media. The voltammetric results showed that while there is no considerable interaction between the two phthalocyanine rings in 4, the splitting of a molecular orbital occurs as a result of the strong interaction between the phthalocyanine rings in 2 and 3.     

Synthesis and characterization of polybinaphthalene incorporating chiral (R) or (S)-1,1′-binaphthalene and oxadiazole units by Heck reaction

Chiral conjugated polymers P-1 and P-2 were synthesized by the polymerization of (R)-3,3′-diiodo-2,2′-bisbutoxy-1,1′-binaphthalene ((R)-M-1) and (S)-3,3′-diiodo-2,2′-bisbutoxy-1,1′-binaphthalene ((S)-M-1) with 2,5-bis(4-vinylphenyl)-1,3,4-oxadiazole (M-2) under Pd-catalyzed Heck coupling reaction, respectively. Both monomers and polymers were analysed by NMR, MS, FT-IR, UV, DSC-TG, fluorescent spectroscopy, GPC and CD spectra. The chiral conjugated polymers exhibit strong Cotton effect in their circular dichroism (CD) spectra indicating a high rigidity of polymer backbone. CD spectra of polymers P-1 and P-2 are almost identical and have opposite signs for their position. These polymers have strong blue fluorescence.     

Ruthenium monoterpyridine complexes with 2,6-bis(benzimidazol-2-yl)pyridine: Synthesis,spectral properties and structure

Ruthenium monoterpyridine complexes with the tridentate 2,6-bis(benzimidazol-2-yl)pyridine (LH₂), [Ru(trpy)(LH₂)]²⁺, [1]²⁺ and [Ru(trpy)(L²⁻)], 2 (trpy = 2,2′:6′,2″-terpyridine) have been synthesized. The complexes have been authenticated by elemental analyses, UV–Vis, FT-IR, ¹H NMR spectra and their single crystal X-ray structures. Complexes [1]²⁺ and 2 exhibit strong MLCT band near 475 and 509 nm, respectively, and are found to be very much dependent on solution pH. The successive pH dependent dissociations of the N–H protons of benzimidazole moiety of LH₂ in [1]²⁺ lead to the formation of 2. The proton induced inter-convertibility of [1]²⁺ and 2 has been monitored via UV–Vis spectroscopy and redox features. The two pK_a values, 5.75 and 7.70, for complex [1]²⁺ have been determined spectroscopically.     

Reactivity of M(en)Cl2 (M = Pd/Pt,en = 1,2-diaminoethane) with N,N′-bis(salicylidene)-p-phenylenediamine: Binding with hexafluorobenzene

Schiff base N,N′-bis(salicylidene)-p-phenylenediamine (LH₂) complexed with Pt(en)Cl₂ and Pd(en)Cl₂ provided [Pt(en)L]₂ · 4PF₆ (1) and Pd(Salen) (2) (Salen = N,N′-bis(salicylidene)-ethylenediamine), respectively, which were characterized by their elemental analysis, spectroscopic data and X-ray data. A solid complex obtained by the reaction of hexafluorobenzene (hfb) with the representative complex 1 has been isolated and characterized as 3 (1 · hfb) using UV–Vis, NMR (¹H, ¹³C and ¹⁹F) data. A solid complex of hfb with a reported Zn-cyclophane 4 has also been prepared and characterized 5 (4 · hfb) for comparison with complex 3. The association of hfb with 1 and 4 has also been monitored using UV–Vis and luminescence data.     

Diterpenes and sesquiterpenes with anti-Coxsackie virus B3 activity from the stems of Illicium jiadifengpi

Seven new diterpenes, jiadifenoic acids J–P (1–7), two new sesquicarane sesquiterpenes, sesquicaranoic acids A and B (8 and 9), and four known compounds, were isolated from the stems of Illicium jiadifengpi. The trans-fused A/B ring junction in diterpenes was deduced from NMR data analysis and confirmed by single-crystal X-ray crystallography of 3. The absolute configurations of compounds 1 and 5 were determined using the Mo₂(OAc)₄-induced circular dichroism (ICD) method. Compounds 8 and 9 are a pair of C-10 epimers, and their absolute configurations were confirmed by analyzing their CD and ICD data. All of the isolated compounds were evaluated in vitro for their antiviral activities against Coxsackie virus B3 (CVB3). Among the isolated compounds, 4, 5, 7, 10, and 11 exhibited reasonable activity against CVB3, with IC₅₀ values of 7.0–22.2 μmol/mL and selective index values (SI=TC₅₀/IC₅₀) of 49.3, 37.1, 31.3, 45.6 and 40.9, respectively.