Optoelectronic and Self‐assembly Properties of Porphyrin Derivatives with Click Chemistry Modification

A series of functionalized porphyrin molecules containing electron‐rich alkynes, synthesized by means of the Sonogashira coupling reaction were further modified by reacting the ethynyl groups with click reagent through a formal [2+2] click reaction. The photophysical and electrochemical properties of the porphyrin derivatives were studied by UV/Vis spectroscopy and cyclic voltammetry. We show that the optoelectronic properties are affected by the click reagent groups and central metal ions. The functionalized porphyrin molecules show strong charge‐transfer (CT) bands in the visible region (near‐IR region) and potent redox activities. Through a phase‐exchange self‐assembly method, the highly organized morphologies were observed by scanning electron microscopy (SEM). The functionalized porphyrin molecules represent an interesting set of candidates for optoelectronic device components. The effect of the metal ions or click reagent groups on the self‐assembly properties were also studied by the UV/Vis spectroscopic titration experiments.     

Thiophene-functionalized isoindigo dyes bearing electron donor substituents with absorptions approaching the near infrared region

A series of six new, highly soluble N,N'-dialkylated isoindigo derivatives bearing different electron donating thiophene units at the 6,6'-positions were synthesized by Stille cross-coupling reaction. The optical and electrochemical properties of these dyes were studied by UV-vis spectroscopy and cyclic voltammetry, revealing a good tunability of their electronic properties by peripheral substituents with amino groups leading to strong absorption reaching the NIR region. The DFT calculations of the frontier molecular orbitals of these dyes corroborate the observed substituent effect on absorption and redox properties.     

Theoretical Studies on the Absorption Spectra and Intramolecular Charge Transfer of Push-pull Zinc Porphyrin Dyes for Dye-sensitized Solar Cells

The electronic structures, absorption spectra and intramolecular charge transfer properties of five push-pull zinc porphyrin analogs with different donor group and π bridge have been investigated by density functio- nal theory(DFT) and TD(time-dependent)-DFT approach. The results show that the asymmetrical substituted diphenylamine group is favorable to the Q-band absorption of porphyrin dyes. The absence of the acetylenic bond in the π bridge part leads to the result that the B-band and the Q-band are blue-shifted and their absorption strength become weaker compared with that containing acetylenic bond, respectively. The introduction of the benzothiadiazole into the π bridge improves the intramolecular charge transfer.     

Preparation of Polyphenylene Ring Derivative Dyes with Wide Wave Absorption Properties and Their Performance Study

Some conjugated benzene ring molecules were prepared using the Sonogashira reaction, and the molecules were post-functionally modified using click chemistry. The optical and electrical band gaps were measured using UV-VIS absorption spectroscopy and the three-electrode method, and the results of both were verified against each other to prove the accuracy of the characterization. In addition, the optical performances of the material were studied by z-scan; almost all materials exhibited good nonlinear optical properties and interconversion between saturable and anti-saturable absorption due to the invocation of click reagents.     

Photoinduced Electron and Energy Transfer in Dyads of Porphyrin Dimer and Perylene Tetracarboxylic Diimide

Two compounds containing a porphyrin dimer and a perylene tetracarboxylic diimide (PDI) linked by phenyl ( 1 ) or ethylene groups ( 2 ) are prepared. The photophysical properties of these two compounds are investigated by steady state electronic absorption and fluorescence spectra and lifetime measurements. The ground state absorption spectra reveal intense interactions between the porphyrin units within the porphyrin dimer, but no interactions between the porphyirn dimer and PDI. The fluorescence spectra suggest efficient energy transfer from PDI to porphyrin accompanied by less efficient electron transfer from porphyrin to PDI. The energy transfer is not affected by the dimeric structure of porphyrin or the linkage between the porphyrin dimer and PDI. However, the electron transfer from porphyrin to PDI is significantly affected by either the linkage between the donor and the acceptor or the polarity of the solvents. The dimeric structure of the porphyrin units in these compounds significantly promotes electron transfer in nonpolar, but not in polar solvents.     

New Dual Donor–Acceptor (2D‐π‐2A) Porphyrin Sensitizers for Stable and Cost‐Effective Dye‐Sensitized Solar Cells

A series of porphyrin sensitizers that featured two electron‐donating groups and dual anchoring groups that were connected through a porphine π‐bridging unit have been synthesized and successfully applied in dye‐sensitized solar cells (DSSCs). The presence of electron‐donating groups had a significant influence on their spectroscopic, electrochemical, and photovoltaic properties. Overall, the dual anchoring groups gave tunable electronic properties and stronger attachment to TiO₂. These new dyes were readily synthesized in a minimum number of steps in gram‐scale quantities. Optical and electrochemical data confirmed the advantages of these dyes for use as sensitizers in DSSCs. Porphyrins with electron‐donating amino moieties provided improved charge separation and better charge‐injection efficiencies for the studied dual‐push–pull dyes. Attenuated total reflectance–Fourier‐transform infrared (ATR‐FTIR) and X‐ray photoelectron spectroscopy of the porphyrin dyes on TiO₂ suggest that both p‐carboxyphenyl groups are attached onto TiO₂, thereby resulting in strong attachment. Among these dyes, cis-Zn2BC2A , with two electron‐donating 3,6‐ditertbutyl‐phenyl‐carbazole groups and dual‐anchoring p‐carboxyphenyl groups, showed the highest efficiency of 4.07 %, with J_SC=9.81 mA cm^?2, V_OC=0.63 V, and FF=66 %. Our results also indicated a better photostability of the studied dual‐anchored sensitizers compared to their mono‐anchored analogues under identical conditions. These results provide insight into the developments of a new generation of high‐efficiency and thermally stable porphyrin sensitizers.     

Optical Properties of New Third-Order Nonlinear Materials Modified by Click Chemistry

A high-yielding click reaction was used to synthesize a series of highly conjugated, symmetrical, as well as asymmetrical compounds with a benzene core. Cyclic voltammetry and ultraviolet/visible absorption spectroscopy were carried out, and proved that the side groups of the benzene derivatives played an important role in the energy gaps, and affected the third-order non-linear optical response. The maximum absorption wavelength of the series of benzene derivatives showed an obvious red-shift. Moreover, the addition of resilient electron-withdrawing groups significantly narrowed the energy levels as compared with precursors. The third-order nonlinear properties of this benzene derivative were tested by the Z-scan technique. The expected properties of this series of molecules were obtained, and it was found that the series of molecules undergoes a transition from reverse saturable absorption to saturable absorption, which has certain reference significance for a nonlinear optical field.     

Synthesis and Photophysical Properties of Doubly β‐to‐β Bridged Cyclic ZnII Porphyrin Arrays

A series of doubly β‐to‐β bridged cyclic Zn^II porphyrin arrays were prepared by a stepwise Suzuki–Miyaura coupling reaction of borylated Zn^II porphyrin with different bridge groups. The coupling of the building block of β,β′‐diboryl Zn^II porphyrin 1 with different bridges provided the doubly β‐to‐β carbazole‐bridged Zn^II porphyrin array 3 , the fluorene‐bridged Zn^II porphyrin array 5 , the fluorenone‐bridged Zn^II porphyrin array 7 , and the three‐carbazole‐bridged Zn^II porphyrin ring 8 . The structural assignment of 3 was confirmed by the X‐ray diffraction analysis, which revealed a highly symmetrical and remarkably bent syn‐form structure. The incorporation of bridge units with different electronic effects results in different photophysical properties of the cyclic Zn^II porphyrin arrays. Comprehensive photophysical studies demonstrate that the electron‐withdrawing bridge fluorenone has the largest electronic interaction with the Zn^II porphyrin unit among the series, thus resulting in the highest two‐photon absorption cross‐section values (σ⁽²⁾) of 6570±60 GM for 7 . The present work provides a new strategy for developing porphyrin‐based optical materials.     

Synthesis and Third‐Order Nonlinear Optical Properties of Triphenylene Derivatives Modified by Click Chemistry

A series of asymmetric triphenylene derivatives containing typical D –π–A structures is successfully synthesized by means of [2+2] cycloaddition–cycloreversion click reactions. The photophysical and electrochemical properties, as well as the click reactions, are characterized by means of UV/Vis absorption spectroscopy, cyclic voltammetry, and DFT modulations. In addition, the third‐order nonlinear properties, including the nonlinear absorption and the nonlinear susceptibilities, are investigated by using Z‐scan techniques. A typical reverse saturable absorption–saturable absorption behavior is observed for the third‐order nonlinear absorption, with the third‐order nonlinear susceptibilities of the compounds being 1.05×10^?12, ?1.50×10^?12, and ?0.52×10^?12 esu, respectively.     

β to β Terpyridylene-bridged porphyrin nanorings

β β to Terpyridine bridged cyclic porphyrin dimer, trimer, tetramer and pentamer were obtained through one-pot Suzuki-Miyaura crossing coupling reaction in good yields with template free. These porphyrin nanorings possess high fluorescence quantum yields and large extinction coefficients.     

Molecular modification of coumarin dyes for more efficient dye sensitized solar cells

In this work, new coumarin based dyes for dye sensitized solar cells (DSSC) have been designed by introducing several substituent groups in different positions of the NKX-2311 structure. Two types of substitutions have been considered: the introduction of three electron-donating groups (-OH, -NH(2), and -OCH(3)) and two different substituents with steric effect: -CH(2)-CH(2)-CH(2)- and -CH(2)-HC=CH-. The electronic absorption spectra (position and width of the first band and absorption threshold) and the position of the LUMO level related to the conduction band have been used as theoretical criteria to evaluate the efficiency of the new dyes. The introduction of a -NH(2) group produces a redshift of the absorption maximum position and the absorption threshold, which could improve the cell efficiency. In contrast, the introduction of -CH(2)-CH(2)-CH(2)- does not modify significantly the electronic structure of NKX-2311, but it might prevent aggregation. Finally, -CH(2)-HC=CH- produces important changes both in the electronic spectrum and in the electronic structure of the dye, and it would be expected as an improvement of cell efficiency for these dyes.     

Structural, optical, and photophysical properties of nickel(II) alkylthioporphyrins: insights from experimental and DFT/TDDFT studies

The ground- and excited-state properties of a Ni(II) porphyrin bearing peripheral alkylthio group, NiOMTP (OMTP = 2,3,7,8,12,13,17,18-octakis methylthio porphyrinate) have been investigated by steady-state and time-resolved absorption spectrometry and DFT/TDDFT theoretical methods. Several conformations corresponding to different deformations of the porphyrin core and to different orientations of the alkylthio groups have been theoretically explored. The nearly degenerate, purely ruffled D(2d) and hybrid (ruffled with a modest degree of saddling) D(2) conformations, both characterized by an up-down (ud) orientation of the vicinal methylthio groups are by far the preferred conformations in the "gas phase". In contrast to NiOEP, it is the orientation of the peripheral substituents rather than the type and degree of distortions of the porphyrin core that determines the stability of the NiOMTP conformers. The ground-state electronic absorption spectra of NiOMTP exhibit significant changes compared to its parent NiP and beta-alkylated analogues, such as NiOEP, resulting in a considerable red shift of the B and the Q bands, intensification and broadening of the Q band, and additional weak absorptions in the region between the Q and B bands. These spectral changes can be understood in terms of the electronic effects of the methylthio groups with nonplanar distortions of the porphyrin ring playing a very minor role. Transient absorption measurements with sub-picosecond resolution performed in toluene and TDDFT calculations reveal that following photoexcitation, NiOMTP deactivates by the pathway 1(pi,pi) --> 3(d(z2),d(x2-y2))--> ground state. The (d,d) state exhibits complex spectral evolution over ca. 8 ps, interpreted in terms of vibrational relaxation and cooling. The cold ligand-field excited state decays with a lifetime of 320 ps. At variance with the highly distorted nickel porphyrins but similar to the planar analogues, the (d,d) spectrum of NiOMTP has transient absorption bands immediately to the red of the bleaching of the ground-state Q and B bands.     

Carotenohematoporphyrins as Tumor-Imaging Dyes. Synthesis and In Vitro Photophysical Characterization*

Multichromophoric dyes for use in tumor imaging have been synthesized and photophysically characterized. Structurally, these dyes are dyads and triads that consist of one or two carotenoid polyenes covalently attached to hematoporphyrin (HP) or hematoporphyrin dimethyl ester (HPDME) moieties via ester linkages. The ground-state absorption of each compound shows that the electronic interaction between the chromophores is small. The fluorescence quantum yield for the dyad monocar-oteno- HPDME is 0.033 and the dicaroteno-HPDME triads have yields between 0.016 and 0.007, all of which are reduced with respect to the parent compound HPDME (0.09). Global analysis of the transient fluorescence decays of the dyads and triads requires two exponential components (?5–6ns and ?1–2ns) to fit the data, while a single exponential component with a lifetime of 9.3 ns describes the decay data of the parent HPDME. Possible mechanisms for the observed porphyrin fluorescence quenching by the nearby carotenoid are discussed. Nanosecond transient absorption reveals a carotene triplet with maximum absorption at 560 nm and a 5.0 μs lifetime. No transient was detected at 450 nm, indicating rapid (10 ns) triplet energy transfer from the hematoporphyrin to the carotenoid moieties in fluid as well as in rigid media. The yield of triplet energy transfer from the porphyrin to the carotenoid moiety is unity. Singlet oxygen, O₂(¹δ_g), studies support the transient absorption data, as none of these compounds is capable of sensitizing O₂(¹δ_g). Liposome vesicles were used to study the photophysical characteristics of the dyes in phospholipid membranes. Singlet oxygen was not sensitized by the dyads and triads in liposomes. Transient absorption measurements suggest that the triads are substantially aggregated within the phospholipid bilayer, whereas aggregation in the dyads is less severe.     

N‐Annulated Perylene‐Substituted and Fused Porphyrin Dimers with Intense Near‐Infrared One‐Photon and Two‐Photon Absorption

Fusion of two N‐annulated perylene (NP) units with a fused porphyrin dimer along the S₀–S₁ electronic transition moment axis has resulted in new near‐infrared (NIR) dyes 1 a / 1 b with very intense absorption (ε>1.3×10⁵ M ^?1 cm^?1) beyond 1250 nm. Both compounds displayed moderate NIR fluorescence with fluorescence quantum yields of 4.4×10^?6 and 6.0×10^?6 for 1 a and 1 b , respectively. The NP‐substituted porphyrin dimers 2 a / 2 b have also been obtained by controlled oxidative coupling and cyclodehydrogenation, and they showed superimposed absorptions of the fused porphyrin dimer and the NP chromophore. The excited‐state dynamics of all of these compounds have been studied by femtosecond transient absorption measurements, which revealed porphyrin dimer‐like behaviour. These new chromophores also exhibited good nonlinear optical susceptibility with large two‐photon absorption cross‐sections in the NIR region due to extended π‐conjugation. Time‐dependent density functional theory calculations have been performed to aid our understanding of their electronic structures and absorption spectra.     

The synthesis and the solvent and substituent effect on the spectroscopic characteristic of 3-ethyl-2-(p-substitued styryl)benzothiazolium iodides

The photophysical and photochemical properties of p-substitued 2-styryl-ethylbenzothiazolium iodides, possessing different electron-withdrawing or electron-donating groups are described. The dyes were prepared by the condensation of 3-ethyl-2-methylbenzothiazole salts with p-substituted benzaldehydes. The synthesis of suitable substrates is presented as well. We describe here the absorption, emission spectra and the luminescence quantum yield of hemicyanine dyes (SH) measured in 11 different organic solvents of varying polarity. Molecular structure of the synthesized dyes was established by (1)H NMR, electronic absorption and fluorescence spectrometry. The spectral data confirmed that all the compounds exist in E-configuration of their styryl residues. The planar molecular conformation is typical for the compounds with five-membered side aromatic moieties (for example benzothiazole). The compounds possessing N-alkyl substituent in phenyl ring, in contrast to the compounds with other substituents, exhibit low fluorescence quantum yield in THF solution. This indicates that for N-alkyl derivatives the non-radiative processes are much more effective than the radiative ones. The electronic absorption and fluorescence emission spectra of tested dyes demonstrate high sensitivity to the nature of substituent introduced into the aromatic ring.     

Toward panchromatic organic functional molecules: density functional theory study on the electronic absorption spectra of substituted tetraanthracenylporphyrins

To achieve full solar spectrum absorption of organic dyes for organic solar cells and organic solar antenna collectors, a series of tetraanthracenylporphyrin derivatives including H(2)(TAnP), H(2)(α-F(4)TAnP), H(2)(β,β'-F(8)TAnP), H(2)(γ,γ'-F(8)TAnP), H(2)(δ,δ'-F(8)TAnP), H(2)[α-(NH(2))(4)TAnP], H(2)[β,β'-(NH(2))(8)TAnP], H(2)[γ,γ'-(NH(2))(8)TAnP], and H(2)[δ,δ'-(NH(2))(8)TAnP] was designed and their electronic absorption spectra were systematically studied on the basis of TDDFT calculations. The nature of the broad and intense electronic absorptions of H(2)(TAnP) in the range of 500-1700 nm is clearly revealed, and different types of π → π* electronic transitions associated with different absorption bands are revealed to correspond to different electron density moving direction between peripherally fused 14-electron-π-conjugated anthracene units and the central 18-electron-π-conjugated porphyrin core. Introduction of electron-donating groups onto the periphery of the H(2)(TAnP) macrocycle is revealed to be able to lead to novel NIR dyes such as H(2)[α-(NH(2))(4)TAnP] and H(2)[δ,δ'-(NH(2))(8)TAnP] with regulated UV-vis-NIR absorption bands covering the full solar spectrum in the range of 300-2400 nm.     

手性锌卟啉的非线性光学性质及对咪唑类客体分子识别的构象研究

在纳秒(ns)领域中，利用Z-扫描技术测定了Zn(o-BocTyr)TAPP(主体1)和Zn(p-BocTyr)TAPP(主体2)两种手性锌卟啉的三阶非线性光学性质以及对咪唑类客体的分子识别行为的构象研究. 结果表明，(1) 两种手性锌卟啉都具有反饱和吸收效应和自散焦效应；(2) 由于两种主体中侧链位置的差异，造成两种主体分子极化程度的不同，主体1具有较大的三阶非线性折射率(n2)值；(3) 主体1中侧链苯环与卟啉环之间存在一定的相互作用；(4) 分子识别出现了配位方向的选择性，客体咪唑(Im)与主体1侧链中的苯环能够形成π-π相互作用，选择从有侧链一方配位于主体1，而2-甲基咪唑(2-MeIm)选择从没有侧链一方进攻主体1，但对于主体2，则没有出现配位方向的选择性.     

Porphyrins for dye-sensitised solar cells: new insights into efficiency-determining electron transfer steps

Porphyrin molecules offer immense potential as the light harvesting component of dye-sensitised nanocrystalline TiO(2) solar cells. Synthetic porphyrin dyes were amongst the first dyes trialled for sensitisation of inorganic semiconducting oxides. Today, they exhibit the best performance reported for dye-sensitised solar cells. Accompanying the significant performance improvement over the last two decades is a much improved understanding of efficiency-determining fundamental electron transfer steps, from charge photogeneration to recombination. In this feature article we highlight our recent discoveries of the influence of porphyrin molecule structure on efficiency determining electron transfer kinetics and device performance by systematically changing the molecular structure and observing electron injection and recombination kinetics using time-resolved optical and electrical probes. Despite our observation of ultrafast charge injection for all porphyrin dyes studied by transient absorption spectroscopy, the injection yield estimated using an internal standard remains below 100% and depends strongly on the molecular structure. The observed discrepancy between kinetic competition and the injection yield is attributed to non-injecting dyes, probably arising due to inhomogeneity. A very interesting sub-ns (0.5 ns to 100 ns) charge recombination channel between photo-injected electrons and porphyrin cations is observed, which is found to be more prominent in free-base porphyrin dyes with a conjugated linker. Charge recombination between the acceptor species in the redox containing electrolyte and injected electrons is shown to be an important limitation of most porphyrin-sensitised solar cells, accelerated by the presence of porphyrin molecules at the TiO(2)-electrolyte interface. This recombination reaction is strongly dependent on the porphyrin molecular structure. Bulky substituents, using a porphyrin dimer instead of a porphyrin monomer, a light soaking treatment of freshly prepared films and co-sensitization of TiO(2) with multiple dyes are shown to be successful strategies to improve electron lifetime. Finally, new developments unique to porphyrin dye-sensitised solar cells, including performance enhancements from a light exposure treatment of a zinc porphyrin dye, a significant performance improvement observed after co-sensitisation of TiO(2) with free-base and zinc porphyrin dyes and the use of porphyrin dimers with increased light harvesting in thin-film TiO(2) solar cells are described.     

Photoinduced electron transfer in platinum(II) terpyridinyl acetylide complexes connected to a porphyrin unit

A series of six new dyads consisting of a zinc or magnesium porphyrin appended to a platinum terpyridine acetylide complex via a para-phenylene bisacetylene spacer are described. Different substituents on the 4' position of the terpyridinyl ligand were explored (OC7H15, PO3Et2, and H). The ground-state electronic properties of the dyads are studied by electronic absorption spectroscopy and electrochemistry, and they indicate some electronic interactions between the porphyrin subunit and the platinum complex. The photophysical properties of these dyads were investigated by steady-state, time-resolved, and femtosecond transient absorption spectroscopy in N,N-dimethylformamide solution. Excitation of the porphyrin unit leads to a very rapid electron transfer (2-20 ps) to the nearby platinum complex followed by an ultrafast charge recombination, thus preventing any observation of the charge separated state. The variation in the rate of the photoinduced electron transfer in the series of dyads is consistent with Marcus theory. The results underscore the potential of the para-phenylene bisacetylene bridge to mediate a rapid electron transfer over a long donor-acceptor distance.     

Allyloxyporphyrin‐Functionalized Multiwalled Carbon Nanotubes: Synthesis by Radical Polymerization and Enhanced Optical‐Limiting Properties

Allyloxyporphyrin‐functionalized multiwalled carbon nanotubes (MWCNT‐TPP) were synthesized by radical polymerization and characterized by FTIR, UV/Vis absorption, and X‐ray photoelectron spectroscopy; elemental analysis; TEM; and thermogravimetric analysis. Z‐scan studies revealed that this nanohybrid exhibits enhanced nonlinear optical (NLO) properties compared to a control sample consisting of a covalently unattached physical blend of MWCNTs and porphyrin, as well as to the separate MWCNTs and porphyrin. At the wavelengths used, the mechanism of enhanced optical limiting likely involves reverse saturable absorption, nonlinear scattering, and photoinduced electron/energy transfer between the MWCNTs and the porphyrin. The role of electron/energy transfer in the NLO performance of MWCNT‐TPP was investigated by Raman and fluorescence spectroscopy.