T → S Energy Transfer in Some Molecular Complexes

Calculations on the bimolecular complexes of acetophenone or benzophenone with anthracene and its substituted derivatives were carried out using a standard quantum-chemical approach to molecular systems. The deactivation pathways for lower triplet excited states of acetophenone and benzophenone were established. The probability of energy transfer from the energy donor to acceptor in the complexes was considered. The analysis of calculation results showed that the T S transfer of electronic excitation energy in these complexes is feasible only in the case of a small distance between the molecules, and the efficiency of this transfer is higher in the acetophenone rather than benzophenone complexes.     

Energy Transfer by a Hopping Mechanism in Dinuclear IrIII/RuII Complexes: A Molecular Wire?

The synthesis and electrochemical and photophysical properties of a series of heterodinuclear ruthenium-iridium complexes linked by a modular para-phenylene bridge [Ir-ph(n)-Ru]3+ (Ir=Ir(ppyFF)2bpy, Ru=Ru(bpy)3, ppyFF=2-(2,4-difluorophenyl)pyridine), bpy=2,2'-bipyridine, ph=phenylene, n=2, 3, 4, 5) are reported. The use of a high-energy iridium complex, which can act as an energy donor when coupled to the lower energy ruthenium-based component, allows the investigation of photoinduced energy transfer from the excited iridium-centre to the ruthenium fragment (energy acceptor). The rate constants of the energy-transfer processes are determined by time-resolved emission and sub-picosecond transient absorption spectroscopy. Interestingly, there is almost no decrease in transfer efficiency or rates as the length between the two chromophores (number of spacers) is increased. This "molecular wire" behavior indicates the dominance of the incoherent hopping mechanism, allowing a very fast energy transfer over long distances (with n = 5 the metal-to-metal distance is estimated to be 32.5 Angstrom). This is the first case in which such behavior is observed for metal complexes, and could lead to new development in molecular electronics.     

The Luminescence Properties and Intramolecular Energy Transfer of Rare Earth Complexes with Aromatic Carboxylic Acids

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Plasmon Effect of Ag Nanoparticles on Förster Resonance Energy Transfer in a Series of Cationic Polymethine Dyes

Theoretical and Experimental Chemistry - Enhanced Förster resonance energy transfer was found for donor–acceptor pairs of cationic dyes in the presences of silver nanoparticles (NPs) in...     

∧-related Quantum Interference of ^2П [Case（a）] Diatom on Rotational Energy Transfer

To study theoretically the relationship between the integral interference angle and the scat- tering angle in collisional quantum interference, the integral interference angle of atom- ^2П[case（a）] diatomic molecules system is described. To simulate the experiment theoretically, the theoretical model on collision-induced rotational energy transfer in an atom- ^2П[case（a）]diatom system is presented based on the first order Born approximation taking into account of the long-range interaction potential. For the ^2П electronic state in the Hund＇s case（a） diatom, the degree of the interference is discussed. The interference angles of collision-induced rotational energy transfer of CN（A^2П） in Hund＇s case（a） with He, Ne, and Ar are calculated quantitatively. The key parameters in the determination of integral interference angles are obtained.     

Photoinduced Electron Transfer in Host-Guest Complexes of Naphthalene Derivatives with p-NBCD and m-NBCD

Photosynthesis plays the most important role for the natural ecosystem as well as for our society. It has evolved over time to prompt ultrafast photoinduced electron transfer from the electronically excited chlorophylls to quinone receptors1-6. Therefore,…     

UV-visible Absorption Studies of Tetrachloro-p-benzoquinone and Tertiary Amines Charge Transfer Complexes in Trichloromethane

TCBiswellknownasnacceptorwhichcanformCTcomplexeswithmanydonormolecules"',andalsocanbeusedintheanalysisandqualitycontrolofdrugsindifferentpharmaceuticaldosageforms3.AlthoughspectrophotometricalmethodisoftenusedtostudythecharacterofCTcomplexes,verylittleresearchonCTcomplexesformedbyTCBandsimpletertiaryaminehavebeenfound.Recently,weemploythespectrophotometricalmethodtoStudytheCTcomplexesusingtheTCBasnacceptorandtertiaryamineasdonors.Inthispaper,wereporttheaboveresultsandexplainsomephenomen…     

Photosensitized Cycloreversion of Cage Compound via Triplet Energy Transfer

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Bonding in [CuNRR′]_4 type clusters

In the past three decades, more than one hundred polynuclear Cu(I) complexes, organometallics and clusters have been synthesized[1]. In many of these compounds there are relatively short Cu-Cu distances of 0.238—0.32 nm (Cu-Cu in metal 0.240 nm). Since Cu(I) has a closed d10 electronic sub-shell, the nature of d10-d10 interactions has also been studied theoretically[2], but the problem whether there is direct or no direct covalent Cu-Cu bonding is still not clear. The same situation also …     

The Synthesis, Luminescence and Energy Transfer of the Binary and Ternary Complexes of Rare Earth with Aminobenzoic Acids and 1,10-Phenanthroline

Inrecentyears.therehasbeenagrowingintereStinthePOtenhalaPPlicahonofeuroPium~terbiumcoordinationcompoundsasltalnescentInaerialandltalnescentprobesforavarietyofchendcalandbiologitalp'Stems[l].ConsiderableinveingationswerefocusedontheltalnescenceproPenies,energi'matchandenergr'transferofaschelateswithochtones[2'3].Howevr,littleattentionha5beenPaidtotheltalnescentlanthanidecomplexeswithcarbonyIicacids14].ComParedtotherareedchelateswith6-diketones.thecomPlexeswitharomaticCarboxylicacidsoffCra…     

A New Product Channel in the Energy Transfer of CO（ a，v'）+ NO（X）

Under single-collision conditions,a beam of metastable molecules CO（ a,v'）generated by DC discharge was allowed to collide with a beam of NO（X）at a fixed angle of 90o . The collision-induced emission from the interaction region was collected at right angles to the beam plane by a lens set and dispersed by a 1 m monochromator where a cooled photomultiplier tube was mounted on the exit slit. The signal from the PMT was transmitted via a discriminator,a photon counter and a boxcar integrator into a computer for storing and processing. Two broadband emissions were observed around the wavelengths of 780 and 860 nm,which can be assigned to NO（b-a） Ogawa bands Δv = + 4 and + 3 sequences,respectively,and referred to the spectroscopic data given by Huber. At the collision energy of 0. 05 eV in the present experimental conditions,the electronic energy of CO（ a,v' = 0）（6. 01 eV）was not enough to excite NO（X）to NO（b,v' = 4,5）（ΔE > 6. 11 eV）. So,what was in act in the energy transfer was the vibrational excitation of CO（a,v' > 0）,and the higher the vibrational excitation of CO（a,v'） was,the stronger the emission intensity of NO（ b-a）could be obtained. It is thought that electron exchange between CO（a）and NO（X）may be operative through the formation of a complex OCNO. The newly discovered formation of NO（ b）channel could be well explained considering the energy conservation,spin conservation and electron exchange mechanism.     

Novel Roles of Metal Ions in Layered Self-assembled Films of Polynuclear Complexes on Their Photoinduced Electron Transfer Properties

Three metal ion bridged self-assembled(SA)films of cis-di(thiocyanato)-bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium were fabricated and characterized by contact angle,UV spectra,cyclic voltammetry and XPS.Theirphotoinduced electron transfer properties(PETP)were examined.Among the titled systems,the highest steady an-odic photocurrent of 1773—1843 nA/cm~1 and the highest quantum yield of 3.2% were achieved.The effects of in-cident light intensity,bias voltage,and electron donor were also studied.The possible mechanism of electron trans-fer was proposed.The results reveal that different metal ion in SA films could affect significantly the photoinducedelectron transfer property.Our experimental results clearly show that bridging metal ions can play both functionaland structural roles in these self-assembled systems.This method of forming functional films can provide a new ap-proach to regulate the property of similar systems.     

Effect of Energy Transfer on UV Spectra of “H-shaped” Azobenzene Derivatives

A series of “H-shaped” organic dimers (azobenzene derivatives) exhibit linear absorption red shift compared with their corresponding monomers experimentally. Dipolar interaction model is not appropriate for the azobenzene derivatives due to the small distance between two “D-π-A” chains. Energy transfer model is suggested for explanation of the absorption red shift. Two necessary conditions for energy transfer were verified. In addition, bi-exponential florescence-delay behavior of the dimer as well as Bella's quantum chemistry calculation shows evidence of energy transfer.     

Inter-Ligand Energy Transfer Process in an Ir-Complex with Expanding π-Conjugated Ligand

The inter-ligand energy transfer (ILET) process in heteroleptic iridium complex, [Ir(dfppy)₂(bpy-Im₂)]⁺ , where dfppy =2-(2,4-difluorophenyl)pyridine and bpy-Im₂ =4,4’-bis(1,2-diphenyl-1H-benzo[d]imidazole)-2,2’,-bipyridine, was investigated using a femtosecond transient absorption (fs-TA) spectroscopic technique. The photophysical properties of [Ir(dfppy)₂(bpy-Im₂)]⁺ with significantly expanding π-conjugated ligand are compared to those of [Ir(dfppy)₂(bpy)]⁺ ( bpy =2,2’-bipyridine) and a free bpy-Im₂ ligand. The emission spectrum of [Ir(dfppy)₂(bpy-Im₂)]⁺ shows no shift upon changing the solvent polarity, whereas the free ligand bpy-Im₂ showed bathochromic fluorescence shifts with increasing solvent polarity, which is attributed to intramolecular charge transfer (ICT). The unique photophysical properties of [Ir(dfppy)₂(bpy-Im₂)]⁺ are due to the fast ILET process from ³MLCT_dfppy to ³MLCT/³LC_bpy-Im2, resulting in the phosphorescence emission originating from ³MLCT/³LC_bpy-Im2. On the other hand, the TA bands of bpy-Im₂ are observed at 540 and 480 nm, corresponding to the singlet and triplet manifolds, respectively. In contrast, the TA spectrum of [Ir(dfppy)₂(bpy-Im₂)]⁺ showes broad bands centered at 420 and 600 nm, attributed to the transitions from ³MLCT_dfppy and ³MLCT/³LC_bpy-Im2, respectively. Time-resolved spectroscopic results confirm the efficient ILET dynamics from ³MLCT_dfppy to ³MLCT/³LC_bpy-Im2 in [Ir(dfppy)₂(bpy-Im₂)]⁺ . From the relaxation times determined by singular value decomposition analysis and simple sequential kinetic model, we infer that the ILET process from ³MLCT_dfppy to ³MLCT/³LC_bpy-Im2 occurs with a time constant of ca. 4 ps. The presented results in this study show that the introduction of an expanding π-conjugated ligand can lead to the efficient ILET dynamics for improving the OLED performance.     

Formation and Photoelectrochemical Properties of Charge Transfer Complexes between Fullerene and Metallophthalocyanine

Fullerelleshavegeneratedarapidlygrowingandactiveresearchareabecauseoftheirunusualstructureandphysico-chemicalproperties.Fullerenes(C,.,.C,,)havehigherelectrollaffinity(2.75ev),soitiswellkllownthattheyareexcellentelectronacceptorsandhavealargenumberofcolljugatedrsbondswhichmayleadtolargenon-linearpolarizabilities'.C,,.,isreportedtoformchargetranstbrcomplexes(CTC)withappropriateelectrondonors,forexample,polymolecularPVK,y-cyclodextrin,aromaticandaliphaticammes'-3.Thecharge-transferinteraction…     

Synthesis of Spirocyclic 1-Pyrrolines from Nitrones and Arynes through a Dearomative [3,3′]-Sigmatropic Rearrangement

A dearomative [3,3′]-sigmatropic rearrangement that converts N-alkenylbenzisoxazolines into spirocyclic pyrroline cyclohexadienones has been developed by using the dipolar cycloaddition of an N-alkenylnitrone and an aryne to access these unusual transient rearrangement precursors. This cascade reaction affords spirocyclic pyrrolines that are inaccessible through dipolar cycloadditions of exocyclic cyclohexenones and provides a fundamentally new approach to novel spirocyclic pyrroline and pyrrolidine motifs that are common scaffolds in biologically-active molecules. Diastereoselective functionalization processes have also been explored to demonstrate the divergent synthetic utility of the unsaturated spirocyclic products.     

Nonequilibrium Solvent Free Energy Curve from Molecular Theory in Electron Transfer Reaction

l.IntroductionEleCtrontransfer(ET)reactionisamongthemostfundaInentalofcheIIilstryandbiochendsny.Thetwrtanroleofevaluationofthes0lventfreeenergyandthercorganhaionenergyaninETprocesshasalwaysbeenreeogfordbyanextensiveliteratureindilsfield[1-2].HeneehowtochooseasuitablesolventreactioncoordinaeandconsequentlyconstructtheassociatedfreeenergyfimtionbecomesthCpriInnysteP,andalsotheaPplicabilityoftheenergygaPlaw.Manyrecentstudiesarefocusedonthesolventpolarizaionandsolventdyndcalbehaviorandmpmeeh…     

Alkylations of Resorcarenes and Calix[4]pyrroles in Phase Transfer Catalytic Systems

Calixlnlarenesarecyclicoligomersmadeupofphenolsandformaldehyde.Thisversatileclassofcompoundshasbeenextensivelystudiedinthelastdecademainlyinordertoobtainnewcomplexingagentsbyappropriatefuntionalizationoftheparentmoleculel.ResorcarenesZandcall-c[4]pyrroles'aretwosubgroupmembersofthefamilyofcalixarensandalsoattractedincreasinginterests.Aspartofaprogrammeaimedatthesynthesisofneweasy-to-makecalixarenemolecules,wedecidedtoinvestigatethealkylationofsomecalixarensinPhaseTransferCatalysis(PTC)condi…     

One-Photon Excitation Followed by a Three-Step Sequential Energy–Energy–Electron Transfer Leading to a Charge-Separated State in a Supramolecular Tetrad Featuring Benzothiazole–Boron-Dipyrromethene–Zinc Porphyrin–C60

A panchromatic triad, consisting of benzothiazole (BTZ) and BF₂-chelated boron-dipyrromethene (BODIPY) moieties covalently linked to a zinc porphyrin (ZnP) core, has been synthesized and systematically characterized by using ¹H NMR spectroscopy, ESI-MS, UV-visible, steady-state fluorescence, electrochemical, and femtosecond transient absorption techniques. The absorption band of the triad, BTZ-BODIPY-ZnP, and dyads, BTZ-BODIPY and BODIPY-ZnP, along with the reference compounds BTZ-OMe, BODIPY-OMe, and ZnP-OMe exhibited characteristic bands corresponding to individual chromophores. Electrochemical measurements on BTZ-BODIPY-ZnP exhibited redox behavior similar to that of the reference compounds. Upon selective excitation of BTZ (≈290 nm) in the BTZ-BODIPY-ZnP triad, the fluorescence of the BTZ moiety is quenched, due to photoinduced energy transfer (PEnT) from ¹BTZ^* to the BODIPY moiety, followed by quenching of the BODIPY emission due to sequential PEnT from the ¹BODIPY* moiety to ZnP, resulting in the appearance of the ZnP emission, indicating the occurrence of a two-step singlet–singlet energy transfer. Further, a supramolecular tetrad, BTZ-BODIPY-ZnP:ImC₆₀, was formed by axially coordinating the triad with imidazole-appended fulleropyrrolidine (ImC₆₀), and parallel steady-state measurements displayed the diminished emission of ZnP, which clearly indicated the occurrence of photoinduced electron transfer (PET) from ¹ZnP* to ImC₆₀. Finally, femtosecond transient absorption spectral studies provided evidence for the sequential occurrence of PEnT and PET events, namely, ¹BTZ^*-BODIPY-ZnP:ImC₆₀→BTZ-¹BODIPY^*-ZnP:ImC₆₀→BTZ-BODIPY-¹ZnP^*:ImC₆₀→BTZ-BODIPY-ZnP^.+:ImC₆₀^.− in the supramolecular tetrad. The evaluated rate of energy transfer, k_EnT, was found to be 3–5×10¹⁰ s⁻¹, which was slightly faster than that observed in the case of BODIPY-ZnP and BTZ-BODIPY-ZnP, lacking the coordinated ImC₆₀. The rate constants for charge separation and recombination, k_CS and k_CR, respectively, calculated by monitoring the rise and decay of C₆₀^.− were found to be 5.5×10¹⁰ and 4.4×10⁸ s⁻¹, respectively, for the BODIPY-ZnP:ImC₆₀ triad, and 3.1×10¹⁰ and 4.9×10⁸ s⁻¹, respectively, for the BTZ-BODIPY-ZnP:ImC₆₀ tetrad. Initial excitation of the tetrad, promoting two-step energy transfer and a final electron-transfer event, has been successfully demonstrated in the present study.