Ethylenic Double Bond Research Articles

Geometric isomerization of dietary monounsaturated fatty acids by a cis/trans fatty acid isomerase from Pseudomonas putida KT2440

Pseudomonas putida KT2440 encodes a defense system that rigidifies membranes by a cytochrome c-type cis/trans fatty acid isomerase (CTI). Despite its potential as an industrial biocatalyst for directly regulating the geometric isomerism of monounsaturated fatty acids, its original catalytic and structural properties have remained elusive. In this study, the catalytic nature of wild-type CTI purified P. putida KT2440 against dietary monounsaturated fatty acids was investigated. It showed substrate preference for palmitoleic acid (C16:1, cis-Δ9), along with substrate promiscuity with chain length and double bond position (palmitoleic acid>cis-vaccenic acid>oleic acid). Under determined optimum reaction conditions, its catalytic efficiency (kcat/Km) was evaluated as 5.13 × 102 M−1·sec−1 against palmitoleic acid. Furthermore, computational predictions of the protein structure revealed its monoheme cytochrome c-type domain and a parasol-like transmembrane domain, suggesting its catalytic mode of action. For effective cis/trans isomerization, the ethylene double bond of monounsaturated fatty acids should be precisely positioned at the heme center of CTI, indicating that its substrate specificity can be determined by the alkyl chain length and the double bond position of the fatty acid substrates. These findings shed light on the potential of CTI as a promising biocatalyst for the food and lipid industry.

A flexible and wearable chemiresistive ethylene gas sensor modified with PdNPs-SWCNTs@Cu-MOF-74 nanocomposite: a targeted strategy for the dynamic monitoring of fruit freshness

A chemiresistive ethylene gas sensor was fabricated for fruit wearable based on SWCNTs/PdNPs/Cu-MOF-74 (SPM) nanocomposite which was attached to a flexible PET substrate (AIEFP) for dynamic monitoring of the freshness of kiwi at room temperature (25 °C). The electrodes are printed on PET substrate by laser direct writing method, which makes the SPM/AIEFP sensor wearable to be attached to the target and achieve accurate in-situ online detection. The sensing mechanism depends on the widely recognized theory of adsorbed oxygen, in which SWCNTs provide a path for charge transfer between materials, PdNPs improve the response by catalyzing the cracking of ethylene double bond and the formation of adsorbed oxygen, and the selective bonding of Cu-MOF-74 and ethylene provides selectivity. The selectivity of the proposed SPM/AIEFP sensor has been proved. Besides, the key parameters of the sensor fabrication were optimized, and the sensing performance was investigated. Finally, the SPM/AIEFP sensor was successfully utilized to determine the ripeness and corruption of kiwifruit in real-time, indicating that the SPM/AIEFP sensor is a good candidate tool for detecting fruit freshness during transportation and storage.

Tuning the competition between photoisomerization and photothermy in biomimetic cyclocurcumin analogues

We report the synthesis and photophysical characterization of biomimetic D-A-D’ cyclocurcumin derivatives, which can potentially be used in light activated chemotherapy. Particularly we highlight that both the donor (D) and acceptor (A) groups significantly influence the photophysical response of the chromophore inducing strong bathochromic shift with D/A strength increase and notable fluorescence quantum yield enhancement with donor strength increase. More important, the nature of the acceptor group (oxo or malonitrile) dramatically modifies the outcome in non-radiative deactivation channels. Indeed, while compounds functionalized with an oxo-moiety undergo ethylenic E → Z photoisomerization, the one bearing a malonitrile group leads exclusively to other non-adiabatic internal conversion channels which much favor photothermal conversion as no isomerization of the ethylenic double bond was observed. The tuning of the photophysical properties and the alteration of isomerization vs photothermal conversion is rationalized through the analysis of the potential energy surfaces along the most relevant degrees of freedom and shows a competitive pathway over malonitrile rotation. Our results offer novel perspective in oxygen-independent light activated chemotherapy and in the control of photochemical processes in biomimetic chromophores.

Epoxidation of Argemone mexicana oil with peroxyacetic acid formed in-situ using sulfated tin (IV) oxide catalyst: Characterization; kinetic and thermodynamic analysis

In this study, sulfated tin (IV) oxide solid acid catalyst was prepared for the epoxidation of Argemone mexicana oil (AMO) with peroxyacetic acid formed in-situ. The catalyst was synthesized using the chemical co-precipitation method and characterized. The effects of various epoxidation parameters on ethylenic double bond conversion (%) and oxygen ring content were analyzed. The maximum ethylenic double bond conversion of 95.5% and epoxy oxygen content of 6.25 was found at the molar ratio of AMO to 30% of H2O2 = 1:2.5, molar ratio of AMO to acetic acid = 1:1.5, catalyst concentration = 12.5%, and reaction temperature = 70 °C at reaction time = 6 h. The kinetic and thermodynamic features of the epoxidation of AMO were also analyzed with appropriate models. The results of the kinetic study of the epoxidation reaction followed pseudo first order with the activation energy = 0.47.03 kJ/mol. Moreover, the thermodynamic constants of epoxidation of AMO were found as ΔH = 44.18 kJ/mol, ΔS = −137.91 Jmol−1k−1) and ΔG = 91.12 kJ/mol. The epoxidized product of AMO was further analyzed using FTIR, 1H NMR, and 13C NMR. The results of these analyses confirmed the successful conversion of the ethylenic double bond in the AMO to EAMO.

Linear and second‐order nonlinear optical properties of non‐fullerene acceptor derivatives with A–D–A structure

AbstractIn this paper, in order to study the relationship between structure and performance, four new non‐fullerene acceptor (NFA) derivatives were designed based on the two reported NFA molecules BO‐4Cl and BTP‐S2 by replacing the benzothiadiazole unit with a less‐electron deficient benzotriazole unit and inserting another ethylene double bond between the central core and the terminal groups. Density functional theory (DFT) and Time‐dependent DFT were applied to investigate linear and nonlinear optical (NLO) properties, such as electronic structure, electronic absorption, reorganization energy, and the second‐order NLO properties. The investigation demonstrates that they are all narrow bandgap derivatives, the absorption spectrum extends to the near‐infrared region and using two ethylene double bond is the most effective way to reduce the energy gap, redshift the maximum absorption peak and the middle absorption band, and enhance second‐order NLO response. Considering the smaller electron and hole reorganization energy and the larger static first hyperpolarizability value, the studied NFA derivatives have great potential to become ambipolar charge transport materials and large second‐order NLO materials.

Synthesis, structure and cytotoxic activity of trans-[PtCl2(EugH)(Caffeine)] and [PtCl(Eug)(Caffeine)] (EugH: eugenol) complexes

Interaction between K[PtCl3(EugH)] (1) and [PtCl(Eug)]2 (2) with Caf afforded two new complexes, trans-[PtCl2(EugH)(Caf)] (3) and [PtCl(Eug)(Caf)] (4), respectively. The procedure to synthesize complex 2 was improved. The structures of two new complexes were characterized by elemental analyses, MS, IR, 1H NMR and NOESY spectroscopies. The result indicated that EugH coordinates with Pt(II) at ethylenic double bond of the allyl group in complex 3, but in complex 4 it is deprotonated and bound with Pt(II) at both the double bond and C5 of the benzene ring. The donor N of caffein is in trans-position in 3 and in cis-position in 4 with respect to the ethylenic double bond. In chloroform solvent, 4 exists in two forms 4a and 4b corresponding to the strong intermolecular hydrogen bond Cl3C-H…ClPt(II) and the strong halogen bond Cl2HC-Cl…Pt(II). The result of testing cytotoxicity of 3 and 4 against four human cancer cells KB, Lu, Hep-G2 and MCF7 showed that complex 3 exhibits good activities on the KB and Hep-G2 with IC50 values of 81,03 and 89,29 μg/mL, respectively.

Quinine di-hydro-chloride hemihydrate.

Numerous non-covalent inter-actions link together discrete mol-ecules in the crystal structure of the title compound, 2C20H26N2O2 2+·4Cl-·H2O {systematic name: 4-[(5-ethenyl-1-azonia-bicyclo-[2.2.2]octan-2-yl)(hy-droxy)meth-yl]-6-meth-oxy-quinolin-1-ium dichloride hemihydrate}. A combination of hydrogen bonding between acidic H atoms and the anions in the asymmetric unit forms a portion of the observed hydrogen-bonded network. π-π inter-actions between the aromatic portions of the cation appear to play a role in the formation of the long-range ordering. One ethyl-ene double bond was found to be disordered. The disorder extends to the neighboring carbon and hydrogen atoms.

Equilibrium Geometries, Adiabatic Excitation Energies and Intrinsic C=C/C–H Bond Strengths of Ethylene in Lowest Singlet Excited States Described by TDDFT

Seventeen singlet excited states of ethylene have been calculated via time-dependent density functional theory (TDDFT) with the CAM-B3LYP functional and the geometries of 11 excited states were optimized successfully. The local vibrational mode theory was employed to examine the intrinsic C=C/C–H bond strengths and their change upon excitation. The natural transition orbital (NTO) analysis was used to further analyze the C=C/C–H bond strength change in excited states versus the ground state. For the first time, three excited states including πy′ → 3s, πy′ → 3py and πy′ → 3pz were identified with stronger C=C ethylene double bonds than in the ground state.

Acetylene/Ethylene Separation and Solid-State Structural Transformation via [2 + 2] Cycloaddition Reactions in 3D Microporous ZnII Metal-Organic Frameworks.

Purification of ethylene by removing acetylene from an ethylene/acetylene (99/1 v/v) mixture is a challenging task in the petrochemical industry. Our effort toward finding new porous materials that can selectively uptake acetylene resulted in two 3D metal-organic frameworks. Compound 1, {[Zn(p-pda)(bpee)]} (p-pda = p-phenylenediacetate and bpee = 1,2-bis(4-pyridyl)ethylene) turned out to be a nonporous structure due to the presence of a bulky and rigid aromatic ring in the p-pda ligand. Interestingly, replacement of p-pda with succinic acid yields the microporous framework {[Zn2(μ3-OH)(suc)1.5(bpee)]·CH3OH·2H2O} (2; suc = succinate), which offers a 1D channel along the a direction occupied by guest methanol and water molecules. Remarkably, the desolvated framework of 2 shows selective uptake of C2H2 over other gas molecules such as C2H4, C2H6, CO2 and CH4 at 293 K. An ideal absorbed solution theory (IAST) study predicts a high selectivity value for acetylene adsorption over the other gas molecules mentioned above. The efficiency of removal of acetylene from ethylene/acetylene mixtures containing 1% acetylene was established through a column breakthrough experiment performed at room temperature. The performance of our material in the purification of ethylene by removing acetylene is comparable with those reported in the literature. In the frameworks of both 1 and 2, the ethylenic double bonds of adjacent bpee linkers are aligned parallel and readily undergo [2 + 2] cycloaddition reactions upon UV-light irradiation to yield {[Zn2(p-pda)2(rctt-tpcb)]} (1IR) and {[Zn4(μ3-OH)2(suc)3(rctt-tpcb)]·2CH3OH·4H2O} (2IR), respectively (rctt-tpcb = regio-cis,trans,trans-tetrakis(4-pyridyl)cyclobutane). Photochemical structural transformations of 100% were observed in single-crystal to single-crystal fashions, which were also supported by 1H NMR spectroscopy. The structures of both 2 and 2IR underwent temperature-dependent reversible structural transformations, which was confirmed by SCXRD and DSC analysis. Selective C2H2 uptake of the dehydrated framework of 2IR was also examined, which demonstrates results similar to those of 2.

Structural, Hirshfeld and DFT studies of conjugated D-π-A carbazole chalcone crystal.

A new conjugated carbazole chalcone compound, (E)-3-[4-(9,9a-di-hydro-8aH-carbazol-9-yl)phen-yl]-1-(4-nitro-phen-yl)prop-2-en-1-one (CPNC), C27H18N2O3, was synthesized using a Claisen-Schmidt condensation reaction. CPNC crystallizes in the monoclinic non-centrosymmetric space group Cc and adopts an s-cis conformation with respect to the ethyl-enic double bonds (C=O and C=C). The crystal packing features C-H⋯O and C-H⋯π inter-actions whose percentage contribution was qu-anti-fied by Hirshfeld surface analysis. Quantum chemistry calculations including geometrical optimization and mol-ecular electrostatic potential (MEP) were analysed by density functional theory (DFT) with a B3LYP/6-311 G++(d,p) basis set.

Photochemical cycloaddition and temperature-dependent breathing in pillared-layer metal–organic frameworks

Single crystallinity of metal–organic frameworks (MOFs) enables the studies of their flexible behaviors with atomic precision. Here, we investigated the structural transformations triggered by photochemical cycloaddition and with temperature-dependent breathing in a series of pillared-layer MOF structures using a variety of pyrazolecarboxylate linkers for the layers and bipyridyl linkers as the pillars. The ethylenic double bonds from the pillars in close proximity undergo quantitative and seteroselective photochemical [2 + 2] cycloaddition upon UV irradiation, transforming the MOFs into structures with cyclobutane-based pillars. Furthermore, reversible breathing of the new pillared-layer MOF was evidenced by the 10.8% unit cell parameter change along c axis upon temperature change between 298 and 173 K. As revealed by single crystal X-ray diffraction, this transformation originates from the relative flattening of the wavy layers upon cooling. These two different types of characteristic structural transformations responding to inherent reactions and external stimuli happen at single crystalline state, providing a well-defined robust system with controlled flexibility.

Descriptors for terpene esters from chromatographic and partition measurements: Estimation of human odor detection thresholds

We have used gas chromatographic retention data together with other data to obtain Abraham descriptors for 30 terpene esters. These include the air-water partition coefficient, as log Kw, for which no experimental values are available for any terpene ester. The other descriptors are the ester dipolarity, S, the hydrogen bond basicity, B, (the ester hydrogen bond acidity is zero for the esters studied), and L the logarithm of the air-hexadecane partition coefficient. Both S and B are larger than those for simple aliphatic esters, as expected from the terpene ester structures that include ring systems and ethylenic double bonds. These descriptors can then be used to obtain a large number of physicochemical and environmental properties of terpene esters. We have analyzed experimental results on human odor detection thresholds and have constructed another equation for the calculation of these thresholds, to go with a previous equation that we have reported. Then the descriptors for terpene esters can be used to estimate the important odor detection thresholds.

Synthesis and structure of organoplatinum(II) complexes containing aryl olefins and 8-hydroxyquinolines

Twelve new organoplatinum(II) complexes: [PtCl(Saf)(2-Me-8-OquiN)] (1), [PtCl(Saf)(5,7-Cl2-8-OquiN)] (2), [PtCl(Saf)(5,7-Cl2-2-Me-8-OquiN)] (3), [PtCl(Meteug)(5,7-Cl2-8-OquiN)] (4), [PtCl(Meteug)(5,7-Cl2-2-Me-8-OquiN)] (5), [Pt(Saf-1H)(2-Me-8-OquiN)] (6), [Pt(Saf-1H)(5,7-Cl2-8-OquiN)] (7), [Pt(Saf-1H)(5,7-Cl2-2-Me-8-OquiN)] (8), [Pt(Eteug-1H)(2-Me-8-OquiN)] (9), [Pt(Eteug-1H)(2-OHC-8-OquiN)] (10), [Pt(Eteug-1H)(5,7-Cl2-8-OquiN)] (11) and [Pt(Eteug-1H)(5,7-Cl2-2-Me-8-OquiN)] (12) (Saf: Safrole, Meteug: Methyl eugenoxyacetate, Saf-1H: Deprotonated safrole, Eteug-1H: Deprotonated ethyl eugenoxyacetate, OquiN: substituted quinolin-8-olate) were synthesized. These complexes were characterized by elemental analyses, IR, 1H NMR, for several also by NOESY, MS spectra and 9 by single-crystal X-ray diffraction. It is shown that in 1-5 the Pt(II) ion is surrounded by a Cl ion and the ethylenic double bond of the aryl olefin, and by N and O atoms of the 8-OquiN, its donor N is in trans-position in comparison with the ethylenic double bond. In 6-12 the Pt(II) ion is surrounded by an aromatic C atom and the ethylenic C = C double bond of the aryl olefin, and by N and O atoms of the 8-OquiN resulting in a slightly distorted square-planar coordination environment; the donor N is in cis-position in comparison with the ethylenic double bond. Complexes 2, 4 and 7 exhibit high activities on human cancer cells KB, Hep-G2, Lu and MCF-7 with most IC50 values lower than those of cisplatin.

Mixed natural arylolefin-quinoline platinum(II) complexes: synthesis, structural characterization and in vitro cytotoxicity studies.

Five new platinum(II) complexes bearing a eugenol and a quinoline derivative, namely [η2-4-allyl-2-methoxy-1-(propoxycarbonylmethoxy)benzene]-trans-dichlorido(quinoline-κN)platinum(II), [PtCl2(C15H20O4)(C9H7N)], (2), {η2-4-allyl-2-methoxy-1-[(propan-2-yloxy)carbonylmethoxy]benzene}-trans-dichlorido(quinoline-κN)platinum(II), [PtCl2(C15H19O4)(C9H7N)], (3), [η2-4-allyl-2-methoxy-1-(propoxycarbonylmethoxy)benzene]chlorido(quinolin-8-olato-κ2N,O)platinum(II), [Pt(C9H6NO)Cl(C15H20O4)], (4), {η2-4-allyl-2-methoxy-1-[(propan-2-yloxy)carbonylmethoxy]benzene}chlorido(quinolin-8-olato-κ2N,O)platinum(II), [Pt(C9H6NO)Cl(C15H20O4)], (5), and [η2-4-allyl-2-methoxy-1-(propoxycarbonylmethoxy)benzene]chlorido(quinolin-2-carboxylato-κ2N,O)platinum(II), [Pt(C10H6NO2)Cl(C15H20O4)], (6), have been synthesized and fully characterized spectroscopically. A single-crystal X-ray diffraction study was carried out for complexes (2) and (4)-(6). PrEug [or 4-allyl-2-methoxy-1-(propoxycarbonylmethoxy)benzene] in (2), (4) and (6), and iPrEug (the propan-2-yloxy analogue of PrEug) in (3) and (5) coordinate with PtII at the ethylenic double bond of the allyl group. In (2)-(6), the donor N atom of the amine group occupies a trans position with respect to the double bond. A comparison of the IC50 values of 0.38-29.23 µM for (2)-(6) with cisplatin, as well as other platinum(II) complexes, indicates an excellent in vitro cytotoxicity against the KB, LU, Hep-G2 and MCF-7 cancer cell lines, with the highest cytotoxic effect (IC50 = 0.38-1.99 µM) being for complexes (4) and (5) bearing a quinolin-8-olate ligand.

Solvent, structural, quantum chemical study and antioxidative activity of symmetrical 1-methyl-2,6-bis[2-(substituted phenyl)ethenyl]pyridinium iodides

15 symmetric 1-methyl-2,6-bis[2-(substituted phenyl)ethenyl]pyridinium iodides were synthesized in this work. Their structures were characterized using IR, 1H and 13C NMR, and UV–Vis spectroscopy. DFT calculations indicated that s-trans/s-trans conformation prevail in all compounds. The effects of specific and non-specific solvent–solute interactions on the UV–Vis absorption maxima shifts were evaluated using linear solvation-free energy relationships (LSER), i.e., Kamlet–Taft and Catalan models. A linear free energy relationship (LFER) in the form of single substituent parameter equations (SSP) was used to postulate quantitative structure–property relations of substituent effect on NMR data. TD-DFT results showed dependence of electronic transition on the substituent effects. The push–pull character of these compounds was analyzed by differences in 13C chemical shift of the ethylenic double bond in 2- and 6-positions of cross-conjugated with pyridinum central ring. Also, the quotient of the occupations for the bonding π and anti-bonding π* orbitals of this bond was considered. Good correlations of the selected parameter between double bond lengths with π*/π and 13C chemical shift differences of the bridging group proved them to be adequate descriptor of push–pull character. Synthesized compounds were screened for the antioxidant activity, using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical methods, and results demonstrated moderate antioxidant potential.

Synthesis, crystal and solution structures of platinacyclic complexes containing eugenol, the main bioactive constituent of Ocimum sanctum L. oil

The dinuclear platinacyclic complex [Pt2Cl2(Eug-1H)2] (1) (Eug-1H = deprotonated eugenol) has been synthesized. Reaction of 1 with amines afforded [PtCl(Eug-1H)(pyridine)] (2), [PtCl(Eug-1H)(4-Me-pyridine)] (3), [PtCl(Eug-1H)(piperidine)] (4), [PtCl(Eug-1H)(quinoline)] (5), [PtCl(Eug-1H)(NH3)] (6), [PtCl(Eug-1H)(4-Me-aniline)] (7), [PtCl(Eug-1H)(4-Cl-aniline)] (8), [Pt(Eug-1H)(8-O-quinoline)] (9) and [Pt(Eug-1H)(8-O-2-Me-quinoline)] (10). X-ray diffraction and NMR analysis show that in complexes 1–10 the chelating eugenol ligand is bound with the Pt(II) ion both through the ethylenic double bond of the allyl group and at a benzene carbon atom; in 2–10 the donor N atom of the amine is in the cis-position with respect to the ethylenic double bond. For complexes 2 and 3, two types of relatively strong highly directional intermolecular interactions are observed in the crystal packing: O–H…ClPt(II) hydrogen bonds and C–H…π interactions, in 3 further complemented by C–H…Cl interactions. The crystal packing of 7 is dominated by dimer formation through O–H…O, N–H…Cl, C–H…Cl and C–H…π interactions. In a d-chloroform solution of 2–5 two types of strong intermolecular interactions were detected: a Cl3C-D…ClPt(II) hydrogen bond and Cl2DC-Cl…Pt(II) halogen bond. Complex 9 exhibits significant activities on the human cancer cells KB, Hep-G2, MCF-7 and Lu, with IC50 values of 8.7, 10.8, 9.9 and 10.4 µM respectively.

Polarity-Dependent Isomerization of an Unsymmetrical Overcrowded Ethylene Promoted by Zwitterionic Contribution in the Twisted Isomer.

The twisted form of bianthrone is known as a metastable state provided by a photo-induced or thermal-induced isomerization of the folded form, and thus prevents the isolation and the detailed analysis of its electronic structure. In this study, an unsymmetrical bianthrone (2), consisting of the electron-withdrawing anthrone and electron-donating acridane, have been synthesized and shown to exhibit a solvent-polarity-dependent isomerization reaction between the folded and twisted isomers. With increasing the polarity of the solvent, 2 showed an isomerization reaction from the folded form to the twisted form. The stabilization of the twisted isomer in polar solvents can be interpreted as proof of its relatively large zwitterionic character. The DMF solution of 2 displayed paramagnetically-broadened NMR signals from the thermally populated triplet state resulting from rotation of the weakened ethylenic double bond of the twisted isomer.

1-{(E)-[(2E)-3-(4-Meth-oxy-phen-yl)-1-phenyl-prop-2-en-1-yl-idene]amino}-3-phenyl-urea: crystal structure and Hirshfeld surface analysis.

The title compound, C23H21N3O2, is constructed about an almost planar disubstituted amino-urea residue (r.m.s. deviation = 0.0201 Å), which features an intra-molecular amine-N-H⋯N(imine) hydrogen bond. In the 'all-trans' chain connecting this to the terminal meth-oxy-benzene residue, the conformation about each of the imine and ethyl-ene double bonds is E. In the crystal, amide-N-H⋯O(carbon-yl) hydrogen bonds connect centrosymmetrically related mol-ecules into dimeric aggregates, which also incorporate ethyl-ene-C-H⋯O(amide) inter-actions. The dimers are linked by amine-phenyl-C-H⋯π(imine-phen-yl) and meth-oxy-benzene-C-H⋯π(amine-phen-yl) inter-actions to generate a three-dimensional network. The importance of C-H⋯π inter-actions in the mol-ecular packing is reflected in the relatively high contributions made by C⋯H/H⋯C contacts to the Hirshfeld surface, i.e. 31.6%.

Excited-State Decay Paths in Tetraphenylethene Derivatives.

The photophysical properties of tetraphenylethene (TPE) compounds may differ widely depending on the substitution pattern, for example, with regard to the fluorescence quantum yield ϕf and the propensity to exhibit aggregation-induced emission (AIE). We report combined electronic structure calculations and nonadiabatic dynamics simulations to study the excited-state decay mechanisms of two TPE derivatives with four methyl substituents, either in the meta position (TPE-4mM, ϕf = 0.1%) or in the ortho position (TPE-4oM, ϕf = 64.3%). In both cases, two excited-state decay pathways may be relevant, namely, photoisomerization around the central ethylenic double bond and photocyclization involving two adjacent phenyl rings. In TPE-4mM, the barrierless S1 cyclization is favored; it is responsible for the ultralow fluorescence quantum yield observed experimentally. In TPE-4oM, both the S1 photocyclization and photoisomerization paths are blocked by non-negligible barriers, and fluorescence is thus feasible. Nonadiabatic dynamics simulations with more than 1000 surface hopping trajectories show ultrafast cyclization upon photoexcitation of TPE-4mM, whereas TPE-4oM remains unreactive during the 1 ps simulations. We discuss the chances for spectroscopic detection of the postulated cyclic photoproduct of TPE-4mM and the relevance of our findings for the AIE process.

Synthesis and spectral characterization of platinum(II) complexes containing eugenol, a natural allylphenol

For the first time, eugenol, a natural bioactive allylphenol, was introduced into coordination with platinum(II) by replacement of ethylene from Zeise’s salt with eugenol (Eug). The obtained complex, K[PtCl3(Eug)] (1), was used as the key compound for preparation of the series of trans-[PtCl2(Eug)(Amine)] (2–11), [PtCl(Eug)(8-O-quinoline)] (12) and [PtCl(Eug)(2-O2C-quinoline)] (13). The synthesized complexes were characterized by elemental analyses, IR, 1H NMR, 13C NMR, HSQS, HMBC, NOESY, and MS spectra. In 1–13 eugenol coordinates with Pt(II) at ethylenic double bond of the allyl group, the donor N of the amines is in trans-position in comparison with the double bond. A display of the trans-effect on the chemical shift of 1H and 13C was remarked. Seven complexes were tested for cell in vitro cytotoxicity on human cancer cells. Complexes 3 and 12 exhibit high activities on Hep-G2 with IC50 = 3.12 and 5.29 μM; 12 gives high activity against KB, Lu and MCF-7 with IC50 = 0.43, 2.95 and 1.84 μM, respectively. Most of these IC50 are lower than those of cisplatin.