Highly fluorescent chameleon nanoparticles and polymer films: multicomponent organic systems that combine FRET and photochromic switching

We describe the preparation of highly efficient stimulus-responsive fluorescence color-tuning in self-assembled supramolecular scaffold systems. The systems consisted of a photochromic compound (BP-BTE) in combination with unique luminescent organic materials (CN-MBE, TPS-CNMBE, TPA-2CNMBE) that exhibited intense fluorescence in the solid state. The emission spectrum was tuned by introducing fluorescence resonance energy transfer and photochromic switching capabilities into the system. The materials were used to successfully demonstrate novel fluorescence patterns that were responsive to multiple stimuli, displayed reversible fluorescence switching, and provided a nondestructive readout of the fluorescence signal.     

Synthesis and photophysical properties of carbazole-based blue light-emitting dendrimers

A new class of highly fluorescent and stable carbazole-based dendrimers (1-5) that contain the ethynylbenzene and diethynylbenzene cores has been synthesized and characterized. They show very high extinction coefficients of absorption (A(max) approximately 328-353 nm) and high quantum yields of fluorescence (lambda(max) approximately 386-437 nm; Phi(F) approximately 0.72-0.89; tau(F) approximately 2.09-3.91 ns) in dichloromethane. The quantum yields of fluorescence of 1-5 in the solid state are equally high (lambda(max) approximately 385-422 nm; Phi(F) approximately 0.40-0.85). These data indicate their potential use as blue-emitting materials in organic light-emitting diodes (OLEDs).     

Photoregulated fluorescence switching in axially coordinated tin(IV) porphyrinic dithienylethene

Photochromic fluorophore Sn(TTP)(DTE)2 , in which two phenolic derivatives of 1,2-dithienylethene are axially coordinated to (5,10,15,20-tetratolylporphyrinato)tin(IV) in trans position, has been synthesized and fully characterized by various spectroscopic methods. We have also investigated the photoregulated fluorescence switching behavior of Sn(TTP)(DTE)2 . The fluorescence of the porphyrin macrocycle in Sn(TTP)(DTE) 2 greatly depends on the state of the 1,2-dithienyletene photochromic switch. In the open state (Sn(TTP)(o-DTE)2), the porphyrin exhibits high fluorescence intensity at 609 and 664 nm when excited at 410 nm. When the photocyclization reaction was carried out by irradiating Sn(TTP)(o-DTE)2 with the UV light (approximately 365 nm), the fluorescence intensity of the porphyrin macrocycle decreased. Back irradiation with visible light at wavelengths greater than 500 nm regenerated Sn(TTP)(o-DTE)2 and almost restored the original fluorescence spectrum. The fluorescence intensity of the porphyrin fluorophore is efficiently regulated by photochromic switching between Sn(TTP)(o-DTE)2 and Sn(TTP)(c-DTE)2 in several cycles, clearly demonstrating that the Sn(TTP)(DTE)2 can act as a system for reversible data processing using fluorescence as the detection method.     

1,10-Phenanthrolines with tunable luminescence upon protonation: a spectroscopic and computational study

We have synthesized nine 2,9-aryl-substituted 1,10-phenanthrolines (1-9) with the aim of rationalizing their electronic absorption and luminescence properties in both the basic and acid form. The latter are generated upon addition of trifluoroacetic acid to CH2Cl2 solutions of 1-9 and their formation is unambiguously evidenced by UV-vis absorption and 1H NMR spectroscopy. 1-9 can be subdivided into three groups, depending on their chemical structure and luminescence behavior. 1-3 are symmetrically substituted p-dianisylphenanthrolines which exhibit relatively intense violet fluorescence in CH2Cl2 (lambda(max) ca. 400 nm, Phi(fl) = 0.12-0.33) and are strongly quenched and substantially red-shifted upon protonation (lambda(max) ca. 550 nm, Phi(fl) = 0.010-0.045). 4-5 are 2,6-dimethoxyphenylphenanthrolines with faint luminescence in both the basic and acid form. 6-9 are various unsymmetric aryl-substituted-phenanthrolines and their relatively strong fluorescence (lambda(max) ca. 400 nm, Phi(fl) = 0.08-0.24) is red-shifted and substantially enhanced following protonation (lambda(max) ca. 475 nm, Phi(fl) = 0.16-0.50). The markedly different trends in the electronic absorption and fluorescence spectra are rationalized by means of both time-dependent Hartree-Fock and density functional theory by using hybrid functionals to assign the excited states. Interestingly, protonation of 1-9 also occurs in spin-coated films simply exposed to vapors of acid, and the reaction can be signaled by the color tuning of the emission signal (vapoluminescence). This observation makes substituted phenanthrolines potential candidates as proton sensors also in the solid phase.     

Enhancement of metal-metal coupling at a considerable distance by using 4-pyridinealdazine as a bridging ligand in polynuclear complexes of rhenium and ruthenium

Novel polynuclear complexes of rhenium and ruthenium containing PCA (PCA = 4-pyridinecarboxaldehyde azine or 4-pyridinealdazine or 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene) as a bridging ligand have been synthesized as PF(6-) salts and characterized by spectroscopic, electrochemical, and photophysical techniques. The precursor mononuclear complex, of formula [Re(Me(2)bpy)(CO)(3)(PCA)](+) (Me(2)bpy = 4,4'-dimethyl-2,2'-bipyridine), does not emit at room temperature in CH(3)CN, and the transient spectrum found by flash photolysis at lambda(exc) = 355 nm can be assigned to a MLCT (metal-to-ligand charge transfer) excited state [(Me(2)bpy)(CO)(3)Re(II)(PCA(-))](+), with lambda(max) = 460 nm and tau < 10 ns. The spectral properties of the related complexes [[Re(Me(2)bpy)(CO)(3)}(2)(PCA)](2+), [Re(CO)(3)(PCA)(2)Cl], and [Re(CO)(3)Cl](3)(PCA)(4) confirm the existence of this low-energy MLCT state. The dinuclear complex, of formula [(Me(2)bpy)(CO)(3)Re(I)(PCA)Ru(II)(NH(3))(5)](3+), presents an intense absorption in the visible spectrum that can be assigned to a MLCT d(pi)(Ru) --> pi(PCA); in CH(3)CN, the value of lambda (max) = 560 nm is intermediate between those determined for [Ru(NH(3))(5)(PCA)](2+) (lambda(max) = 536 nm) and [(NH(3))(5)Ru(PCA)Ru(NH(3))(5)](4+) (lambda(max) = 574 nm), indicating a significant decrease in the energy of the pi-orbital of PCA. The mixed-valent species, of formula [(Me(2)bpy)(CO)(3)Re(I)(PCA)Ru(III)(NH(3))(5)](4+), was obtained in CH(3)CN solution, by bromine oxidation or by controlled-potential electrolysis at 0.8 V in a OTTLE cell of the [Re(I),Ru(II)] precursor; the band at lambda(max) = 560 nm disappears completely, and a new band appears at lambda(max) = 483 nm, assignable to a MMCT band (metal-to-metal charge transfer) Re(I) --> Ru(III). By using the Marcus-Hush formalism, both the electronic coupling (H(AB)) and the reorganization energy (lambda) for the metal-to-metal intramolecular electron transfer have been calculated. Despite the considerable distance between both metal centers (approximately 15.0 Angstroms), there is a moderate coupling that, together with the comproportionation constant of the mixed-valent species [(NH(3))(5)Ru(PCA)Ru(NH(3))(5)](5+) (K(c) approximately 10(2), in CH(3)CN), puts into evidence an unusual enhancement of the metal-metal coupling in the bridged PCA complexes. This effect can be accounted for by the large extent of "metal-ligand interface", as shown by DFT calculations on free PCA. Moreover, lambda is lower than the driving force -DeltaG degrees for the recombination charge reaction [Re(II),Ru(II)] --> [Re(I),Ru(III)] that follows light excitation of the mixed-valent species. It is then predicted that this reverse reaction falls in the Marcus inverted region, making the heterodinuclear [Re(I),Ru(III)] complex a promising model for controlling the efficiency of charge-separation processes.     

Porphyrin, phthalocyanine and porphyrazine derivatives with multifluorenyl substituents as efficient deep-red emitters

The synthesis and photophysical properties are described for a series of porphyrin, phthalocyanine and pyrazinoporphyrazine derivatives which bear four or eight peripheral fluorenyl substituents as antennae. Representative examples are 5,10,15,20-tetra(9,9-dihexyl-9H-fluoren-2-yl)porphyrin (2), 5,10,15,20-tetrakis[4-(9,9-dihexyl-9H-fluoren-2-yl)phenyl]porphyrin (3), 2,3,9,10,16,17,23,24-octakis(9,9-dihexyl-9H-fluoren-2-yl)-29H,31H-phthalocyanine (8) and 2,3,9,10,16,17,23,24-octakis[4-(9,9-dihexyl-9H-fluoren-2-yl)phenyl]-29H,31H-tetrapyrazinoporphyrazine (9). Palladium-mediated Suzuki-Miyaura cross-coupling reactions have been key steps for attaching the substituents. The compounds are deep-red emitters: lambda(max)(em)=659 (3), 737 (8) and 684 nm (9). Their absorption and emission spectra, their fluorescence lifetimes and quantum yields are correlated with the structures of the macrocycles and the substituents. The solution fluorescence quantum yields of porphyrin derivatives substituted with fluorene (2-4) and terphenyl substituents (7) (Phi(f)=0.21-0.23) are approximately twice that of tetraphenylporphyrin. For phthalocyanine derivative 8, Phi(f) was very high (0.88). Specific excitation of the fluorene units of 8 produced emission from both of them (lambda(max)=480 nm) and also from the phthalocyanine core (lambda(max)=750 nm), indicating a competitive rate of energy transfer and radiative decay of the fluorenes. Organic light-emitting devices (OLEDs) were made by spin-coating techniques by using a polyspirobifluorene (PSBF) copolymer as the host blended with 3 (5 wt. %) in the configuration ITO/PEDOT:PSS/PSBF copolymer:3/Ca/Al. Deep-red emission (lambda(max)=663 nm; CIE coordinates x=0.70, y=0.27) was observed with an external quantum efficiency of 2.5 % (photons/electron) (at 7.5 mA cm(-2)), a low turn-on voltage and high emission intensity (luminance) of 5500 cd m(-2) (at 250 mA/ m(2)).     

Ligand effects on luminescence of new type blue light-emitting mono(2-phenylpyridinato)iridium(III) complexes

Newly prepared hydrido iridium(III) complexes [Ir(ppy)(PPh3)2(H)L](0,+) (ppy = bidentate 2-phenylpyridinato anionic ligand; L = MeCN (1b), CO (1c), CN(-) (1d); H being trans to the nitrogen of ppy ligand) emit blue light at the emission lambda(max) (452-457, 483-487 nm) significantly shorter than those (468, 495 nm) of the chloro complex Ir(ppy)(PPh3)2(H)(Cl) (1a). Replacing ppy of 1a-d with F2ppy (2,4-difluoro-2-phenylpyridinato anion) and F2Meppy (2,4-difluoro-2-phenyl-m-methylpyridinato anion) brings further blue-shifts down to the emission lambda(max) at 439-441 and 465-467 nm with CIE color coordinates being x = 0.16 and y = 0.18-0.20 to display a deep-blue photoemission. No significant blue shift is observed by replacing PPh3 of 1a with PPh2Me to produce Ir(ppy)(PPh2Me)2(H)(Cl) (1aPPh 2Me), which displays emission lambda max at 467 and 494 nm. The chloro complexes, [Ir(ppy)(PPh3)2(Cl)(L)](0,+) (L = MeCN (2b), CO (2c), CN(-) (2d)) having a chlorine ligand trans to the nitrogen of ppy also emit deep-blue light at emission lambda(max) 452-457 and 482-487 nm.     

Synthesis and self-association, absorption, and fluorescence properties of differentially functionalized hexakis(p-substituted-phenylethynyl)benzenes

The dual Sonogashira coupling reactions of 1,3,5-tribromo-2,4,6-triiodobenzene with p-X-phenylacetylene followed by another p-Y-phenylacetylene (X, Y = OSiMe(2)Bu-t or CO(2)Et) produced a series of differentially functionalized hexakis(p-substituted-phenylethynyl)benzenes with D(3)(h)() symmetry (3h: 1,3,5-X-2,4,6-Y) and C(2)(v)() symmetry (3g,i: 1,2,3,5-X-4,6-Y; 3f,j: 1-X-2,3,4,5,6-Y). In a similar manner, 1,3,5-tris(p-X-phenylethynyl)-2,4,6-tris(p-Y-phenylethynyl)benzenes and 1,2,3,5-tetrakis(p-X-phenylethynyl)-4,6-bis(p-Y-phenylethynyl)benzenes (3l: X = OSiMe(2)Bu-t, Y = NO(2); 3m,n: X = N(n-octyl)(2), Y = NO(2); 3o,p: X = N(n-octyl)(2), Y = CH(OCH(2)CH(2)O); 3q,r: X = N(n-octyl)(2), Y = CHO; 3s,t: X = N(n-octyl)(2), Y = CH=C(CN)(2)) were prepared. Compounds 3 with electron-withdrawing groups self-aggregated by a pi-pi stacking interaction and solvophobic effect. In the absorption and fluorescence spectra of 3, lambda(max)(abs) and lambda(max)(em) showed red shifts as the donor-acceptor dipole at the end functional groups of the para position was increased. In the absorption spectra, lambda(max)(abs) showed red shifts upon increasing the number of combination of electron-donating and -withdrawing groups on the diagonal line in a molecule, whereas lambda(max)(em) in the fluorescence spectra exhibited red shifts upon decreasing the molecular symmetry.     

卟啉-二芳基乙烯分子的合成及其无损读取性能

二噻吩乙烯是一类性能优良的有机光致变色化合物,在信息储存领域具有广阔的应用前景,本文以2-甲基噻吩、苯甲醛和吡咯为原料,经过多步反应合成了1-(2-甲基-3-噻吩基)-2-{2-甲基-5-{4-[4-(10,15,20-三苯基-5-卟啉基)苯基]氨基羰基苯基}-3-噻吩基}环戊烯(DTE-TPP),其结构经核磁共振波谱仪(NMR)、质谱(MS)和傅里叶变换红外光谱仪(FTIR)表征确认,通过紫外-可见光谱研究了化合物的光致变色性能、抗疲劳性,并辅以荧光光谱探究了化合物的无损读取功能。结果表明,该化合物在254和660 nm的光照射下,发生可逆的光致变色反应,重复光照8次后其紫外-可见光谱与初始谱图相比无明显差异,显示出良好的抗疲劳性;当激发光为520 nm时,开、闭环异构体有较高的荧光对比度,有望实现数据的无损读取。     

Theoretical Study and Luminescence Properties of the Cyclic Cu(3)(dppm)(3)OH(2+) Cluster. The First Luminescent Cluster Host at Room Temperature

The [Cu(3)(dppm)(3)OH](BF(4))(2) cyclic cluster host is found to be luminescent at 298 K (lambda(max) = 540 nm; tau(e) = 89 +/- 9 &mgr;s; Phi(e) = 0.14 +/- 0.01) in degassed ethanol solutions and at 77 K (lambda(max) = 480 nm; tau(e) = 170 +/- 40 &mgr;s; Phi = 0.73 +/- 0.07) also in ethanol. The nature of the lowest energy excited states has been addressed theoretically using density functional theory and experimentally using UV-visible, luminescence, and polarized luminescence spectroscopy and is found to be (1,3)A(2) arising from the.(18e)(4)(7a(2))(1)(13a(1))(1) electronic configuration. The excited state geometry optimization for the model Cu(3)(PH(3))(6)OH(2+) compound in its T(1) state ((3)A(2)) has been performed using density functional theory and compared to its ground state structure. The Cu.Cu bond length is expected to decrease greatly in the excited state (calculated DeltaQ approximately 0.47 ?), in agreement with the d(10) electronic configuration. The perturbation of the photophysical properties by the addition of two guest carboxylate anions has been investigated. From the Stern-Volmer plots, the quenching constants, k(q), are 1.65 x 10(8) and 5.10 x 10(8) M(-)(1) s(-)(1) for acetate and 4-aminobenzoate, respectively, which are also proportional to the relative binding strengths of the substrates with Cu(3)(dppm)(3)OH(2+) (i.e., acetate < 4-aminobenzoate).     

5' modification of duplex DNA with a ruthenium electron donor-acceptor pair using solid-phase DNA synthesis

Incorporation of metalated nucleosides into DNA through covalent modification is crucial to measurement of thermal electron-transfer rates and the dependence of these rates with structure, distance, and position. Here, we report the first synthesis of an electron donor-acceptor pair of 5' metallonucleosides and their subsequent incorporation into oligonucleotides using solid-phase DNA synthesis techniques. Large-scale syntheses of metal-containing oligonucleotides are achieved using 5' modified phosporamidites containing [Ru(acac)(2)(IMPy)](2+) (acac is acetylacetonato; IMPy is 2'-iminomethylpyridyl-2'-deoxyuridine) (3) and [Ru(bpy)(2)(IMPy)](2+) (bpy is 2,2'-bipyridine; IMPy is 2'-iminomethylpyridyl-2'-deoxyuridine) (4). Duplexes formed with the metal-containing oligonucleotides exhibit thermal stability comparable to the corresponding unmetalated duplexes (T(m) of modified duplex = 49 degrees C vs T(m) of unmodified duplex = 47 degrees C). Electrochemical (3, E(1/2) = -0.04 V vs NHE; 4, E(1/2) = 1.12 V vs NHE), absorption (3, lambda(max) = 568, 369 nm; 4, lambda(max) = 480 nm), and emission (4, lambda(max) = 720 nm, tau = 55 ns, Phi = 1.2 x 10(-)(4)) data for the ruthenium-modified nucleosides and oligonucleotides indicate that incorporation into an oligonucleotide does not perturb the electronic properties of the ruthenium complex or the DNA significantly. In addition, the absence of any change in the emission properties upon metalated duplex formation suggests that the [Ru(bpy)(2)(IMPy)](2+)[Ru(acac)(2)(IMPy)](2+) pair will provide a valuable probe for DNA-mediated electron-transfer studies.     

Mechanism of the Photodissociation of 4-Diphenyl(trimethylsilyl)methyl-N,N-dimethylaniline

On irradiation in hexane (248- and 308-nm laser light) 4-diphenyl(trimethylsilyl)methyl-N,N-dimethylaniline, 2, undergoes photodissociation of the C-Si bond giving 4-N,N-dimethylamino-triphenylmethyl radical, 3(*) (lambda(max) at 343 and 403 nm), in very high quantum yield (Phi = 0.92). The intervention of the triplet state of 2 (lambda(max) at 515 nm) is clearly demonstrated through quenching experiments with 2,3-dimethylbuta-1,3-diene, styrene, and methyl methacrylate using nanosecond laser flash photolysis (LFP). The formation of 3(*) is further demonstrated using EPR spectroscopy. The detection of the S(1) state of 2 was achieved using 266-nm picosecond LFP, and its lifetime was found to be 1400 ps, in agreement with the fluorescence lifetime (tau(f) = 1500 ps, Phi(f) = 0.085). The S(1) state is converted almost exclusively to the T(1) state (Phi(T) = 0.92). In polar solvents such as MeCN, 2 undergoes (1) photoionization to its radical cation 2(*)(+), and (2) photodissociation of the C-Si bond, giving radical 3(*) as before in hexane. The formation of 2(*)(+) occurs through a two-photon process. Radical cation 2(*)(+) does not fragment further, as would be expected, to 3(*) via a nucleophile(MeCN)-assisted C-Si bond cleavage but regenerates the parent compound 2. Obviously, the bulkiness of the triphenylmethyl group prevents interaction of 2(*)(+) with the solvent (MeCN) and transfer to it of the electrofugal group Me(3)Si(+). The above results of the laser flash photolysis are supported by pulse radiolysis, fluorescence measurements, and product analysis.     

Automated synthesis of 3'-metalated oligonucleotides

We report the first synthesis of a metallonucleoside bound to a solid support and subsequent oligonucleotide synthesis with this precursor. Large-scale syntheses of metal-containing oligonucleotides are achieved using a solid support modified with [Ru(bpy)(2)(impy')](2+) (bpy is 2,2'-bipyridine; impy' is 2'-iminomethylpyridyl-2'-deoxyuridine). A duplex formed with the metal-containing oligonucleotide exhibits superior thermal stability when compared to the corresponding unmetalated duplex (T(m) = 50 degrees C vs T(m) = 48 degrees C). Electrochemical (E(1/2) = 1.3 V vs NHE), absorption (lambda(max) = 480 nm), and emission (lambda(max) = 720 nm, tau = 44 ns, Phi = 0.11 x 10(-)(3)) data for the ruthenium-modified oligonucleotides indicate that the presence of the oligonucleotide does not perturb the electronic properties of the ruthenium complex. The absence of any change in the emission properties upon duplex formation suggests that the [Ru(bpy)(2)(impy)](2+) chromophore will be a valuable probe for DNA-mediated electron-transfer studies. Despite the relatively high Ru(III/II) reduction potential, oxidative quenching of photoexcited [Ru(bpy)(2)(impy)](2+) does not lead to oxidative damage of guanine or other DNA bases.     

(Pyridine)pentaamminechromium(III). Synthesis, Characterization, and Photochemistry

The Cr(NH(3))(5)(py)(3+) ion has been obtained by metathesis of Cr(NH(3))(5)(Me(2)SO)(3+) in pyridine, isolated as the perchlorate salt, and characterized by absorption (lambda(max) at 467, 352, and 260 nm) and emission spectra (lambda(max) at 668 nm, tau = 2.0 &mgr;s at 20 degrees C in water) and by the py aquation rate (k = 5 x 10(-)(4) s(-)(1) at 80 degrees C). Ligand-field (LF) band irradiation in acid aqueous solution (10(-)(2) M HClO(4)) induces photoaquation of py (Phi = 0.26) and NH(3) (Phi = 0.16). HPLC indicates that the latter reaction gives rise to both cis- and trans-Cr(NH(3))(4)(py)(H(2)O)(3+), with the predominance of the cis isomer. This is the first Cr(NH(3))(5)X(z+)() species where Phi(x) > Phi(NH)3: the result is compared with the predictions of various photolysis models and is taken as chemical evidence for pi-acceptance by the py ligand. The photostereochemistry is also discussed. The phosphorescence is totally quenched by Cr(C(2)O(4))(3)(3)(-) (k(q) = 2.7 x 10(9) M(-)(1) s(-)(1)), while the photoreactions are only in part. On 470-nm excitation, the Phi(py)/Phi(NH)()3 ratio is approximately 1 and approximately 2 for the unquenchable and the quenchable contributions, respectively. Such a difference, suggesting at least two reactive precursors, can be interpreted in terms of the photochemistry proceeding from either the lowest doublet and quartet excited states or, alternatively, from the (4)E and (4)B(2) states. Irradiation of the very distinct absorption of coordinated pyridine results in both doublet-state emission and loss of py and NH(3). Comparison of this photobehavior with the LF results gives an efficiency of 0.7 for conversion of the py-localized pipi states into the Cr-localized LF states, confirmed by the wavelength dependence of the relative emission yields. Some py release (Phi = 0.03) is concluded to originate in the pipi states.     

Electrical properties of 1,4-bis(4-(phenylethynyl)phenylethynyl)benzene and its application for organic light emitting diodes

We found that a phenylene ethynylene derivative, 1,4-bis(4-(phenylethynyl)phenylethynyl)benzene (BPPB), provides very high photoluminescence efficiency both in solution (Phi(PL) = 95 +/- 3%) and thin films (Phi(PL) = 71 +/- 3%); further, we observed blue electroluminescence (EL) of lambda(EL(max)) approximately 470 and 510 nm with an external EL efficiency of eta(EL) approximately 0.53% and maximum luminance of approximately 70000 cd m(-2) at current density of approximately 2 A cm(-2) with BPPB as an emitter; also we identified that BPPB functions as a hole transport layer in organic light emitting diodes.     

Ultraviolet photolysis of HCHO: absolute HCO quantum yields by direct detection of the HCO radical photoproduct

Absolute quantum yields for the radical (H + HCO) channel of HCHO photolysis, Phi(HCO), have been measured for the tropospherically relevant range of wavelengths (lambda) between 300 and 330 nm. The HCO photoproduct was directly detected by using a custom-built, combined ultra-violet (UV) absorption and cavity ring down (CRD) detection spectrometer. This instrument was previously employed for high-resolution (spectral resolution approximately 0.0035 nm) measurements of absorption cross-sections of HCHO, sigma(HCHO)(lambda), and relative HCO quantum yields. Absolute Phi(HCO) values were measured at seven wavelengths, lambda = 303.70, 305.13, 308.87, 314.31, 320.67, 325.59, and 329.51 nm, using an independent calibration technique based on the simultaneous UV photolysis of HCHO and Cl(2). These Phi(HCO) measurements display greater variability as a function of wavelength than the current NASA-JPL recommendations for Phi(HCO). The absolute Phi(HCO)(lambda) determinations and previously measured sigma(HCHO)(lambda) were used to scale an extensive set of relative HCO yield measurements. The outcome of this procedure is a full suite of data for the product of the absolute radical quantum yield and HCHO absorption cross-section, Phi(HCO)(lambda)sigma(HCHO)(lambda), at wavelengths from 302.6 to 331.0 nm with a wavelength resolution of 0.005 nm. This product of photochemical parameters is combined with high-resolution solar photon flux data to calculate the integrated photolysis rate of HCHO to the radical (H + HCO) channel, J(HCO). Comparison with the latest NASA-JPL recommendations, reported at 1 nm wavelength resolution, suggests an increased J(HCO) of 25% at 0 degrees solar zenith angle (SZA) increasing to 33% at high SZA (80 degrees). The differences in the calculated photolysis rate compared with the current HCHO data arise, in part, from the higher wavelength resolution of the current data set and highlight the importance of using high-resolution spectroscopic techniques to achieve a complete and accurate picture of HCHO photodissociation processes. All experimental Phi(HCO)(lambda)sigma(HCHO)(lambda) data are available for the wavelength range 302.6-331.0 nm (at 294 and 245 K and under 200 Torr of N(2) bath gas) as Supporting Information with wavelength resolutions of 0.005, 0.1, and 1.0 nm. Equivalent data sets of Phi(H(2)+CO)(lambda)sigma(HCHO)(lambda) for the molecular (H(2) + CO) photofragmentation channel, produced using the measured Phi(HCO)(lambda) sigma(HCHO)(tau) values, are also provided at 0.1 and 1.0 nm resolution.     

吡啶基二噻吩乙烯轴向配位锰(Ⅱ)-卟啉化合物的合成及性质

针对有机光致变色材料实际应用中存在的光量子产率低,抗疲劳性差,记录信息在读取后遭到破坏等瓶颈问题,本文以2-甲基噻吩为原料,经过卤代、傅克酰基化、Mc Murry环合和Suzuki偶联反应得到的1-(5-氯-2-甲基噻吩-3-基)-2-(5-吡啶基-2-甲基噻吩-3-基)-环戊烯与锰(Ⅱ)-四苯基卟啉反应合成了吡啶基二噻吩乙烯轴向配位锰(Ⅱ)-卟啉化合物,通过紫外可见(UV-Vis)吸收光谱研究了其光致变色性能和抗疲劳性,并结合荧光光谱对无损读取功能进行了探究。实验结果表明,该化合物具有良好的光致变色性能及优良的抗疲劳性,通过波长为254、490和550 nm的光调控可无损地实现信息的写-读-擦过程,该物质有望应用于二进制存储设备中。     

萘并吡喃光致变色荧光开关研究进展

萘并吡喃及其衍生物是经典的光致变色材料,具有很低的背景颜色、优良的光致变色抗疲劳性、易于调控的变色动力学、开环体具有宽的吸收等优点,受到了研究者的重视。本文综述了近几年来作者课题组利用萘并吡喃构建光致变色荧光开关的研究进展,通过将荧光基团和萘并吡喃以掺杂模式、共聚物和有机小分子等形式构建光致变色荧光开关,研究了它们在溶液和薄膜中的荧光开关性能,初步探讨了萘并吡喃荧光开关在非破坏性读出和荧光成像等方面的应用潜能。     

Photoluminescence properties of four-coordinate gold(I)-phosphine complexes of the types [Au(diphos)2]PF6 and [Au2(tetraphos)2](PF6)2

Numerous reports describe the photoluminescence of two- and three-coordinate gold(I)-phosphine complexes, but emission in their analogous four-coordinate complexes is almost unknown. This work examines the luminescence of tetrahedral gold(I) complexes of the types [Au(diphos)(2)]PF(6) (diphos = 1,2-bis(diphenylphosphino)ethane, 1) and [Au(2)(tetraphos)(2)](PF(6))(2) (tetraphos = (R,R)-(+/-)/(R,S)-1,1,4,7,10,10-hexaphenyl-1,4,7,10-tetraphosphadecane, (R,R)-(+/-)/(R,S)-2). Although nonemitting in solution, these complexes luminesce with an intense yellow color (lambda(max) 580-620 nm) at 293 K in the solid state or when immobilized as molecular dispersions within solid matrixes. The excited-state lifetimes of the emissions (tau 4.1-9.4 micros) are markedly dependent on the inter- and intramolecular phenyl-phenyl pairing interactions present. At 77 K in an ethanol glass, two transitions are observed: a minor emission at lambda(max) 415-450 nm and a major emission at lambda(max) 520-595 nm. For [Au(1)(2)]PF(6), lifetimes of tau 251.0 +/- 20.5 micros were determined for the former transition and tau 14.9 +/- 4.6 micros for the latter. Density functional theory (DFT) calculations and comparative studies indicate that the former of these emissions involves triplet LMCT pi(Ph) --> Au(d)-P(p) transitions associated with individual P-phenyl groups. The latter emissions, which are the only ones observed at 293 K, are assigned to LMCT pi(Ph-Ph) --> Au(d)-P(p) transitions associated with excited P-phenyl dimers. Other tetrahedral gold(I)-phosphine complexes containing paired P-Ph substituents display similar emissions. The corresponding phosphine ligands, whether free, protonated, or bound to Ag(I), do not exhibit comparable emissions. Far from being rare, luminescence in four-coordinate Au(I)-phosphine complexes appears to be general when stacked P-phenyl groups are present.     

Photolabile ruthenium nitrosyls with planar dicarboxamide tetradentate N(4) ligands: effects of in-plane and axial ligand strength on NO release

Four ruthenium nitrosyls, namely [(bpb)Ru(NO)(Cl)] (1), [(Me(2)bpb)Ru(NO)(Cl)] (2), [(Me(2)bpb)Ru(NO)(py)](BF(4)) (3), and [(Me(2)bqb)Ru(NO)(Cl)] (4) (H(2)bpb = 1,2-bis(pyridine-2-carboxamido)benzene, H(2)Me(2)bpb = 1,2-bis(pyridine-2-carboxamido)-4,5-dimethylbenzene, H(2)Me(2)bqb = 1,2-bis(quinaldine-2-carboxamido)-4,5-dimethylbenzene; H is the dissociable amide proton), have been synthesized and characterized by spectroscopy and X-ray diffraction analysis. All four complexes exhibit nu(NO) in the range 1830-1870 cm(-)(1) indicating the [Ru-NO](6) configuration. Clean (1)H NMR spectra in CD(3)CN (or (CD(3))(2)SO) confirm the S = 0 ground state for all four complexes. Although the complexes are thermally stable, they release NO upon illumination. Rapid NO dissociation occurs when solutions of 1-3 in acetonitrile (MeCN) or DMF are exposed to low-intensity (7 mW) UV light (lambda(max) = 302 nm). Electron paramagnetic resonance (EPR) spectra of the photolyzed solutions display anisotropic signals at g approximately 2.00 that confirm the formation of solvated low-spin Ru(III) species upon NO release. The ligand trans to bound NO namely, anionic Cl(-) and neutral pyridine, has significant effect on the electronic and NO releasing properties of these complexes. Change in the in-plane ligand strength also has effects on the rate of NO release. The absorption maximum (lambda(max)) of 4 is significantly red shifted (455 nm in DMF) compared to the lambda(max) values of 1-3 (380-395 nm in DMF) due to the extension of conjugation on the in-plane ligand frame. As a consequence, 4 is also sensitive to visible light and release NO (albeit at a slower rate) upon illumination to low-intensity visible light (lambda > 465 nm). Collectively, the photosensitivity of the present series of ruthenium nitrosyls demonstrates that the extent of NO release and their wavelength dependence can be modulated by changes of either the in-plane or the axial ligand (trans to bound NO) field strength.