Fluoride ion-triggered dual fluorescence switch based on naphthalimides winged zinc porphyrin

A novel fluoride ion-triggered dual fluorescence molecular switch based on naphthalimides winged zinc porphyrin (1) was designed and prepared. The fluorescence of the zinc porphyrin unit could be regulated "ON-OFF" on the excitation of 365 nm and "OFF-ON" on the excitation of 504 nm, respectively, in the presence of fluoride ion. The obvious color changes induced by the intermolecular proton transfer on N-H fragments are clearly visible to the naked eye.     

Near-infrared luminescence from platinum(II) diimine compounds

Square-planar Pt(II) complexes of the bis(mesitylimino)acenaphthene (mesBIAN) ligand are emissive from a MMLL'CT excited state in a dichloromethane solution at room temperature. Investigation of the nature of the frontier orbitals in these near-IR emitters by a combination of emission spectroscopy, electron paramagnetic resonance spectroscopy, and density functional theory calculations suggests that emission is enabled by the presence of low-lying ligand pi* orbitals on the mesBIAN.     

A robust microporous zinc porphyrin framework solid

A robust microporous zinc(II) metalloporphyrin framework solid has been synthesized. The proposed structural model developed from X-ray single crystal data has an interpenetrated three-dimensional framework of zinc trans-biscarboxylate tetraarylporphyrins whose carboxylates coordinate the six edges of tetrahedral Zn(4)O(6+) clusters, maintaining a charge-neutral framework. This cubic framework has 74% free volume and 4 x 7 A pores. N(2) adsorption gives a type I isotherm with a surface area of 800 m(2)/g, which is greater than that of a typical zeolite. Experimental evidence indicates that the interpenetrated frameworks of the evacuated solid remain intact and retain a microporous structure. This is a versatile framework system: alteration of the metal in the porphyrin may create a catalytically active solid, and modification of the 10-, 20-substituents of the porphyrin can provide control over both the polarity and the size of the pores.     

Near-infrared luminescence of nine-coordinate neodymium complexes with benzimidazole-substituted 8-hydroxyquinolines

A new class of benzimidazole-substituted 8-hydroxyquinoline ligands has been prepared that contain a monoanionic tridentate N,N,O-coordinating unit. These ligands form charge-neutral lanthanide complexes of the type [Ln(L-R) 3]. nH 2O or [Ln 2(L2) 3]. nH 2O ( n = 1-3) with early lanthanides from La (III) to Gd (III) inclusive. Crystallographic characterization was carried out for 11 complexes with 6 different ligands. In all of these structures, the lanthanide ion was found to be nine-coordinated by three ligands arranged in an "up-up-down" fashion around the metal center. The coordination environment can be described as a tricapped trigonal prism, with N atoms of quinoline rings occupying capping positions. Upon deprotonation of the ligand and complex formation, a new absorption band appears in the visible range of the spectrum with a maximum in the range of 466-483 nm and molar absorption coefficient of (7.2 - 18) x 10 (3) M (-1) cm (-1). Its origin is likely to be an intraligand phenolate-to-pyridyl charge transfer transition centered on the 8-hydroxyquinolate chromophore. Upon excitation in ligand absorption bands, new Nd (III) complexes display characteristic metal-centered luminescence in the near-infrared region from 850 to 1450 nm with quantum yields and lifetimes in solid state at room temperature as high as 0.34% and 1.2 mus, respectively.     

Preliminary study on dual fluorescence behavior of porphyrin

It is well known that porphyrin derivatives play a key role in the primary process of photo-synthesis[1], in which porphyrins directly absorb the sunlight or indirectly acquire excitation en-ergy from light-harvesting antenna system to reach their excited state, and then donate electrons to quinone acceptors to yield a series of charge-separated species. In general, only first singlet ex-cited state of porphyrins is involved in energy transfer process[2]. However, highly excited state (S2 stat…     

Influence of nonplanarity and extended conjugation on porphyrin basicity

Thermodynamic basicities of several new nonplanar water soluble tetraaryltetracyclohexano- (Ar(4)TCHP) and tetraaryltetrabenzoporphyrins (Ar(4)TBP) have been measured and correlated with their structural parameters. While the degrees of nonplanarity in these porphyrins are similar, Ar(4)TCHPs exhibit significantly higher basicities than Ar(4)TBPs and than planar tetraarylporphyrins. Low basicities of distorted Ar(4)TBPs are believed to be due to extended pi-conjugation, which causes delocalization of the core electron density in these porphyrins and reduces negative charges at the protonation site.     

Yb-邻非啰啉-曙红三元配合物近红外发光测定Yb3+

介绍了Yb-邻菲啰啉-曙红三元配合物的发光性质,并应用这一特性建立了一种新的Yb3+的分析方法.研究结果表明这一三元配合物具有良好的发光特性,曙红对Yb3+发光具敏化作用.测定Yb3+的检出限可达8.0×10-7 moL/L,线性范围为8.0×10-7～2.6×10-5 moL/L, 回收率为102%.     

Femto-picosecond relaxation of triazole-bridged bis(zinc porphyrin)

The femtosecond dynamics of excitation relaxation has been revealed for the zinc porphyrin dimer using the pump-probe technique. The data obtained have been analyzed with the use of quantum-chemical calculations. The excitation relaxation dynamics shows that systems of this kind hold promise as models for investigation of photosystems and development of artificial analogues of natural photosynthetic centers. A model has been proposed to explain the found coherent dynamics of exciton bands.     

Coordination dimer based on zinc octaethylporphyrin and meso-pyridyl-substituted porphyrin

Russian Journal of General Chemistry - New dimeric porphyrin was synthesized as a result of coordination interaction between 2,3,7,8,12,13,17,18-octaethylporphyrinatozinc(II) and...     

Two-dimensionally extended porphyrin tapes: synthesis and shape-dependent two-photon absorption properties

We report the synthesis and characterization of L- and T-shaped porphyrin tapes as extensible structural motifs of two-dimensionally extended porphyrin tapes. The two-photon absorption (TPA) cross-section values (sigma((2))) for L- and T-shaped porphyrin tapes as well as those for linear trimeric and tetrameric porphyrin tapes were measured by an open-aperture Z-scan method at 2300 nm, a wavelength at which the one-photon absorption contribution is either zero or almost negligible. Under these conditions, the sigma((2)) values for the linear porphyrin tape trimer and tetramer were determined to be 18 500 and 41 200 GM, respectively. The sigma((2)) value for the L-shaped trimer was determined to be 8700 GM, which is only half that of the linear trimer, whereas the sigma((2)) value for the T-shaped tetramer was measured to be 35 700 GM. These results clearly indicate the dependence of the TPA cross-section on the molecular shape, which underscores the importance of directionality in the pi-conjugation pathway for the enhancement of TPA cross- section.     

Foldamer-based pyridine-fullerene tweezer receptors for enhanced binding of zinc porphyrin

This paper reports the design and synthesis of a new series of hydrogen bonding-mediated foldamer-derived tweezer receptors that are used for efficient complexation of zinc porphyrin guest. One end of the rigidified aromatic amide backbone is incorporated with one fullerene unit, while another end is connected to one pyridine or imidazole unit. The ¹H NMR, UV-vis, and fluorescent investigations in chloroform revealed that, due to the intramolecular hydrogen bonding-driven preorganized folded conformation, the fullerene and pyridine units of the receptors are located with suitable spatial separation and consequently able to co-complex zinc porphyrin with remarkably increased stability. In contrast, the imidazole-incorporated receptor displays a weakened binding affinity possibly due to structural mismatching and large steric hindrance. The association constants of the complexes of the new receptors with zinc porphyrin have been determined.     

Dis-aggregation of an insoluble porphyrin in a calixarene matrix: characterization of aggregate modes by extended dipole model

In this paper, the different aggregation modes of a water-insoluble porphyrin (EHO) mixed with an amphiphilic calix[8]arene (C8A), at the air-water interface and in Langmuir-Blodgett (LB) film form, are analyzed as a function of the mixed composition. The strategy used to control the EHO aggregation has consisted of preparing mixed thin films containing EHO and C8A, in different ratios, at the air-water interface. Therefore, the increase of the C8A molar ratio in the mixed film diminishes the aggregation of the EHO molecules, although such an effect must be exclusively related to the dilution of the porphyrin. The reflection spectra of the mixed C8A-EHO films registered at the air-water interface, show a complex Soret band exhibiting splitting, hypochromicity and broadening features. Also, during the transfer process at high surface pressure, it has been shown that the EHO molecules are ejected from the C8A monolayer and only a fraction of porphyrin is transferred to the solid support, in spite of a complete transfer for the C8A matrix. The complex structure of the reflection spectra at the air-water interface, as well as the polarization dependence of the absorption spectra for the mixed LB films, indicate the existence of four different arrangements for the EHO hosted in the C8A matrix. The aggregate formation is governed by two factors: the attraction between the porphyrin rings which minimizes their separation, and the alkyl chain interactions, that is, hydrophobic effect and/or steric hindrance which determine and restrict the possible aggregation structures. By using the extended dipole model, the assignment of the spectral peaks observed to different EHO aggregates is shown.     

Laser photolysis of zinc porphyrin dissolved in cyanohexylbiphenyl liquid crystal

A laser photolysis study of ZnTPP (P) oriented in nematic and isotropic cyanohexylbiphenyl (6CB) as a function of added 1.4-benzoquinone (Q) is reported. In the absence of Q, enhancement of triplet absorption below the clearing point (nematic phase) is observed. It is attributed to the improved alignment of the optical transition in the ordered matrix and also to the increase in the intersystem crossing efficiency. T−S₁. In the presence of Q in the nematic phase. An additional increase in triplet absorption is noticed. This result is interpreted in terms of a triplet radical pair [P^+√…Q^−√]^T,RP formation which is facilitated by the ordering in the liquid crystal, thus providing an additional channel for triplet formation. The triplet P^T in 6CB (nematic or isotropic) is quenched with a second-order rate of ≈10⁸ M⁻¹ s⁻¹ as compared to 2 × 10⁹ M⁻¹ s⁻¹ in toluene.     

High-dimensional zinc porphyrin nanoframeworks as efficient radiosensitizers for cervical cancer

Radiotherapy is widely used clinically, but the toxic and side effects of nonselective killing of high-energy radiation limit its application. Finding biocompatible materials to assemble radiotherapy sensitizers and studying their sensitization patterns are of great significance for the clinical application. Here, biocompatible zinc porphyrin was chosen as sub-unit to construct various dimensional coordination frameworks. By employing top-down approach, suitable nanoframeworks with various dimensional zinc porphyrin were synthesized as radiosensitizers. The experimental data showed that high-dimensional zinc porphyrin nanoframeworks exhibit higher X-ray response performance.     

Absorption and luminescence spectra of zinc mesotetraphenyl-2,3-tetraphenanthrenoporphin

The electronic absorption and luminescence spectra are affected by the extension of the conjugated system in a tetrapyrrole macroring on account of aromatic-ring annelation, which has been examined for mesotetraphenyl-2,3-tetraphenanthrenoporphin and the zinc complex of it. Fluorescence and phosphorescence characteristics have been measured. The phenanthrene-nucleus annelation to the porphyrin macroring affects the features of the S₁ and T₁ lowest excited states in the same way as the attachment of naphthalene rings in positions 2 and 3 to the latter.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 1, pp. 92–97, January–February, 1990.     

Charge transport in photofunctional nanoparticles self-assembled from zinc 5,10,15,20-tetrakis(perylenediimide)porphyrin building blocks

Molecules designed to carry out photochemical energy conversion typically employ several sequential electron transfers, as do photosynthetic proteins. Yet, these molecules typically do not achieve the extensive charge transport characteristic of semiconductor devices. We have prepared a large molecule in which four perylene-3,4:9,10-tetracarboxydiimide (PDI) molecules that both collect photons and accept electrons are attached to a central zinc 5,10,15,20-tetraphenylporphyrin (ZnTPP) electron donor. This molecule self-assembles into ordered nanoparticles both in solution and in the solid-state, driven by van der Waals stacking of the PDI molecules. Photoexcitation of the nanoparticles results in quantitative charge separation in 3.2 ps to form ZnTPP(+)PDI(-) radical ion pairs, in which the radical anion rapidly migrates to PDI molecules that are, on average, 21 A away, as evidenced by magnetic field effects on the yield of the PDI triplet state that results from radical ion pair recombination. These nanoparticles exhibit charge transport properties that combine important features from both photosynthetic and semiconductor photoconversion systems.     

Directed assembly of chiral organometallic squares that exhibit dual luminescence

Chiral molecular squares based on the Pt-alkynyl linkage were synthesized via stepwise directed assembly, and exhibit interesting dual luminescence at room temperature which is potentially exploitable for chiral sensory applications.