A large pi-conjugated chromophore composed of two dipyrido[3,2-a:2’,3’-c]phenazine (dppz) units directly fused to the central tetrathiafulvalene (TTF) core, has been prepared as a bridging ligand, and its strong binding ability to Ru2+ forming a new dinuclear complex is presented. The electronic absorption and luminescence and the electrochemical behaviour of the free ligand as well as the Ru2+ complex have been investigated in detail. The free ligand shows a very strong band in the UV region consistent with ligand centred π-π* transitions and an intense broad band in the visible region corresponding to an intramolecular charge transfer (ILCT) transition. Upon coordination, a metal-to-ligand charge transfer (MLCT) appears at 22520 cm-1 while the ILCT band is bathochromically shifted by 1620 cm-1. These electrochemically amphoteric chromophores have also been characterized by spectroelectrochemical methods. The oxidized radical species of the free ligand show a strong tendency to undergo aggregation, in which long-distance attractive interactions overcome the electrostatic repulsion. Moreover, these two new chromophores reveal an ILCT fluorescence with large solvent-dependent Stokes shifts and quantum efficiencies of 0.052 for the free ligand and 0.016 for its dinuclear Ru2+ complex in CH2Cl2.
  • A Pt(II) complex with both a phenanthroline and a tetrathiafulvalene-extended dithiolate ligand: Synthesis, crystal structure, electro-chemical and spectroscopic properties
    C. Jia, J. Ding, S.-X. Liu, G. Labat, A. Neels, A. Hauser and S. Decurtins
    Polyhedron, 55 (2013), p87-91
    DOI:10.1016/j.poly.2013.02.064 | unige:32100 | Article HTML | Article PDF
The reaction of 4,5-bis(2'-cyano-ethylsulfanyl)-4',5'-dipropylthiotetrathiafulvalene with [Pt(phen)Cl2] (phen = 1,10-phenanthroline) with CsOH as base in CH3OH–THF affords the target complex 1 in 44% yield. This complex crystallizes in the monoclinic space group P21/c, M = 790.01, a = 12.1732(12), b = 15.851(2), c = 14.5371(16) Å, b = 107.693(12)˚, V = 2672.4(5) Å3 and Z = 4. It undergoes two reversible single-electron oxidation and two irreversible reduction processes. An intense electronic absorption band at 15200 cm-1 (658 nm) in CH2Cl2 is assigned to the intramolecular mixed metal/ligand-to-ligand charge transfer (LLCT) from a tetrathiafulvalene-extended dithiolate-based HOMO to a phenanthroline-based LUMO. This band shifts hypsochromically with increasing solvent polarity. Systematic changes in the optical spectra upon oxidation allow precise tuning of the oxidation states of 1 and reversible control over its optical properties. Irradiation of 1 at 15625 cm-1 (640 nm) in glassy solution below 150 K results in emission from the 3LLCT excited state.
  • Synthesis and Redox and Photophysical Properties of Benzodifuran–Spiropyran Ensembles
    H. Li, J. Ding, S. Chen, C. Beyer, S.-X. Liu, H.-A. Wagenknecht, A. Hauser and S. Decurtins
    Chemistry - A European Journal, 19 (20) (2013), p6459-6466
    DOI:10.1002/chem.201204043 | unige:27859 | Abstract | Article PDF
Two benzodifuran (BDF)-coupled spiropyran (SP) systems and their BDF reference compounds were obtained in good yields through Huisgen–Meldal–Sharpless “click” chemistry and then subjected to investigation of their electrochemical and photophysical properties. In both SP and merocyanine (MC) forms of the coupled molecules, the BDF-based emission is quenched to around 1 % of the quantum yield of emission from the BDF reference compounds. Based on electrochemical data, this quenching is attributed to oxidative electron-transfer quenching. Irradiation at 366 nm results in ring opening to the MC forms of the BDF-coupled SP compounds and the SP reference compound with a quantum efficiency of about 50 %. The rate constants for the thermal ring closing are approximately 3.4×10−3 s−1. However, in the photostationary states the MC fractions of the coupled molecules are substantially lower than that of the reference SP compound, attributed to the observed acceleration of the ring-closing reaction upon irradiation. As irradiation at 366 nm invariably also excites higher-energy transitions of the BDF units in the coupled compounds, the ring-opening reaction is accelerated relative to the SP reference, which results in lower MC fractions in the photostationary state. Reversible photochromism of these BDF-coupled SP compounds renders them promising in the field of molecular switches.
  • Tetrathiafulvalene-Benzothiadiazoles as Redox-Tunable Donor-Acceptor Systems: Synthesis and Photophysical Study
    F. Pop, A. Amacher, N. Avarvari, J. Ding, L.M. Lawson Daku, A. Hauser, M. Koch, J. Hauser, S.-X. Liu and S. Decurtins
    Chemistry - A European Journal, 19 (7) (2013), p2504-2514
    DOI:10.1002/chem.201202742 | unige:26401 | Abstract | Article PDF
Electrochemical and photophysical analysis of new donor–acceptor systems 2 and 3, in which a benzothiadiazole (BTD) unit is covalently linked to a tetrathiafulvalene (TTF) core, have verified that the lowest excited state can be ascribed to an intramolecular-charge-transfer (ICT) π(TTF)→π*(benzothiadiazole) transition. Owing to better overlap of the HOMO and LUMO in the fused scaffold of compound 3, the intensity of the 1ICT band is substantially higher compared to that in compound 2. The corresponding CT fluorescence is also observed in both cases. The radical cation TTF+. is easily observed through chemical and electrochemical oxidation by performing steady-state absorption experiments. Interestingly, compound 2 is photo-oxidized under aerobic conditions.
  • A Donor–Acceptor Tetrathiafulvalene Ligand Complexed to Iron(II): Synthesis, Electrochemistry, and Spectroscopy of [Fe(phen)2(TTF-dppz)](PF6)2
    N. Dupont, Y.-F. Ran, S.-X. Liu, J. Grilj, E. Vauthey, S. Decurtins and A. Hauser
    Inorganic Chemistry, 52 (1) (2013), p306-312
    DOI:10.1021/ic3019277 | unige:25113 | Abstract | Article HTML | Article PDF
The synthesis and photophysical properties of the complex [Fe(phen)2(TTF-dppz)]2+ (TTF-dppz = 4′,5′-bis-(propylthio)tetrathiafulvenyl[i]dipyrido[3,2-a:2′,3′-c]phenazine, phen = 1,10-phenanthroline) are described. In this complex, excitation into the metal–ligand charge transfer bands results in the population of a high-spin state of iron(II), with a decay lifetime of approximately 1.5 ns, in dichloromethane, at room temperature. An intraligand charge transfer state can also be obtained and has a lifetime of 38 ps. A mechanism for the different states reached is proposed based on transient absorption spectroscopy.
  • Targeting π-Conjugated Multiple Donor–Acceptor Motifs Exemplified by Tetrathiafulvalene-Linked Quinoxalines and Tetrabenz[bc,ef,hi,uv]ovalenes: Synthesis, Spectroscopic, Electrochemical, and Theoretical Characterization
    H.-P. Jia, J. Ding, Y.-F. Ran, S.-X. Liu, C. Blum, I. Petkova, A. Hauser and S. Decurtins
    Chemistry - An Asian Journal, 6 (12) (2011), p3312-3321
    DOI:10.1002/asia.201100515 | unige:18010 | Abstract | Article PDF
An efficient synthetic approach to a symmetrically functionalized tetrathiafulvalene (TTF) derivative with two diamine moieties, 2-[5,6-diamino-4,7-bis(4-pentylphenoxy)-1,3-benzodithiol-2-ylidene]-4,7-bis(4-pentylphenoxy)-1,3-benzodithiole-5,6-diamine (2), is reported. The subsequent Schiff-base reactions of 2 afford large π-conjugated multiple D–A arrays, for example the triad 2-[4,9-bis(4-pentylphenoxy)-1,3-dithiolo[4,5-g]quinoxalin-2-ylidene]-4,9-bis(4-pentylphenoxy)-1,3-dithiolo[4,5-g]quinoxaline (8) and the corresponding tetrabenz[bc,ef,hi,uv]ovalene-fused pentad 1, in good yields and high purity. The novel redox-active nanographene 1 is so far the largest known TTF-functionalized polycyclic aromatic hydrocarbon with a well-resolved 1H NMR spectrum. The electrochemically highly amphoteric pentad 1 and triad 8 exhibit various electronically excited charge-transfer states in different oxidation states leading to intense optical intramolecular charge transfer (ICT) absorbances over a wide spectral range. The chemical and electrochemical oxidations of 1 result in an unprecedented TTF•+ radical cation dimerization, leading to the formation of [1•+]2 at room temperature in solution due to the stabilizing effect arising from strong π–π interactions. Moreover, ICT fluorescence is observed with large solvent-dependent Stokes shifts and quantum efficiencies of 0.05 for 1 and 0.035 for 8 in CH2Cl2.
  • Effect of the Addition of a Fused Donor−Acceptor Ligand on a Ru(II) Complex: Synthesis, Characterization, and Photoinduced Electron Transfer Reactions of [Ru(TTF-dppz)2(Aqphen)]2+
    N. Dupont, Y.-F. Ran, H.-P. Jia, J. Grilj, J. Ding, S.-X. Liu, S. Decurtins and A. Hauser
    Inorganic Chemistry, 50 (8) (2011), p3295-3303
    DOI:10.1021/ic101951n | unige:15004 | Abstract | 2(Aqphen)]2+" target="_blank">Article HTML | Article PDF
The synthesis and the photophysical properties of the complex [Ru(TTF-dppz)2(Aqphen)]2+(TTF = tetrathiafulvalene, dppz = dipyrido-[3,2-a:2′,3′-c]phenazine, Aqphen = anthraquinone fused to phenanthroline via a pyrazine bridge) are described. In this molecular triad excitation into the metal−ligand charge transfer bands results in the creation of a long-lived charge separated state with TTF acting as electron donor and anthraquinone as terminal acceptor. The lifetime of the charge-separated state is 400 ns in dichloromethane at room temperature. A mechanism for the charge separation involving an intermediate charge-separated state is proposed based on transient absorption spectroscopy.
  • An Electrochemical and Photophysical Study of a Covalently Linked Inorganic–Organic Dyad
    A. Kahnt, L.-P. Heiniger, S.-X. Liu, X. Tu, Z. Zheng, A. Hauser, S. Decurtins and D.M. Guldi
    ChemPhysChem, 11 (2010), p651-658
    DOI:10.1002/cphc.200900728 | unige:6465 | Abstract | Article PDF
A molecular donor-acceptor dyad comprising a hexarhenium cluster core, [Re63-Se)8]2+, and a fullerene moiety which are covalently linked through a pyridine ligand was synthesized and fully characterized. The electrochemical and photophysical properties are reported. The detailed study includes cyclic voltammetry, steady-state absorption and fluorescence spectroscopy, radiation chemistry and transient absorption spectroscopy. A light-induced electron transfer between the inorganic cluster moiety and the fullerene can be excluded. However, a light-induced energy transfer from the rhenium cluster to the fullerene is proposed.
  • A Compactly Fused π-Conjugated Tetrathiafulvalene-Perylenediimide Donor-Acceptor Dyad
    M. Jaggi, C. Blum, N. Dupont, J. Grilj, S.-X. Liu, J. Hauser, A. Hauser and S. Decurtins
    Organic Letters, 11 (14) (2009), p3096-3099
    DOI:10.1021/ol901186n | unige:3553 | Abstract | Article HTML | Article PDF
The synthesis and structural characterization of a tetrathiafulvalene-fused perylenediimide molecular dyad is presented. Its largely extendedπ-conjugation provides intense optical absorption bands over a wide spectral range. The planar functional molecule exhibits a short-livednonluminescent excited state attributed to intramolecular charge separation.
In order to study the electronic interactions in donor-acceptor ensembles as a function of pH, an efficient synthetic route to three imidazole-annulated tetrathiafulvalene (TTF) derivatives 1-3 is reported. Their electronic absorption spectra, in view of photoinduced intramolecular charge transfer, and their electrochemical behavior were investigated, and pKa values for the two protonation processes on the acceptor unit were determined in organic solvents by photometric titration. The influence of the TTF moiety on these values is discussed.
  • Pronounced Electrochemical Amphotericity of a Fused Donor–Acceptor Compound: A Planar Merge of TTF with a TCNQ-Type Bithienoquinoxaline
    X. Gugano, A.L. Kanibolotsky, C. Blum, S.F.L. Mertens, S.-X. Liu, A. Neels, H. Hagemann, P.J. Skabara, S. Leutwyler, T. Wandlowski, A. Hauser and S. Decurtins
    Chemistry - A European Journal, 15 (1) (2009), p63-66
    DOI:10.1002/chem.200802011 | unige:3555 | Abstract | Article HTML | Article PDF
Electronic absorption spectrum of 1 in DMF solution at room temperature, together with the calculated oscillator strengths.
  • Ruthenium(II) Coordination Chemistry of a Fused Donor-Acceptor Ligand: Synthesis, Characterization and Photoinduced Electron Transfer Reactions of [{Ru(bpy)2}n(TTF-ppb)](PF6)2n (n = 1, 2)
    C. Goze, N. Dupont, E. Beitler, C. Leiggener, H. Jia, P. Monbaron, S.-X. Liu, A. Neels, A. Hauser and S. Decurtins
    Inorganic Chemistry, 47 (23) (2008), p11010-11017
    DOI:10.1021/ic801252t | unige:3564 | Abstract | Article HTML | Article PDF
A π-extended, redox-active bridging ligand 4′,5′-bis(propylthio)tetrathiafulvenyl[i]dipyrido[2,3-a:3′,2′-c]phenazine (L) was prepared via direct Schiff-base condensation of the corresponding diamine−tetrathiafulvalene (TTF) precursor with 4,7-phenanthroline-5,6-dione. Reactions of L with [Ru(bpy)2Cl2] afforded its stable mono- and dinuclear ruthenium(II) complexes 1 and 2. They have been fully characterized, and their photophysical and electrochemical properties are reported together with those of [Ru(bpy)2(ppb)]2+ and [Ru(bpy)2(μ-ppb)Ru(bpy)2]4+ (ppb = dipyrido[2,3-a:3′,2′-c]phenazine) for comparison. In all cases, the first excited state corresponds to an intramolecular TTF → ppb charge-transfer state. Both ruthenium(II) complexes show two strong and well-separated metal-to-ligand charge-transfer (MLCT) absorption bands, whereas the 3MLCT luminescence is strongly quenched via electron transfer from the TTF subunit. Clearly, the transient absorption spectra illustrate the role of the TTF fragment as an electron donor, which induces a triplet intraligand charge-transfer state (3ILCT) with lifetimes of approximately 200 and 50 ns for mono- and dinuclear ruthenium(II) complexes, respectively.
  • Synthesis of new ethynylbipyridine-linked mono- and bis-tetrathiafulvalenes: electrochemical, spectroscopic, and Ru(II)-binding studies
    C. Goze, S.-X. Liu, C. Leiggener, L. Sanguinet, E. Levillain, A. Hauser and S. Decurtins
    Tetrahedron, 64 (7) (2008), p1345-1350
    DOI:10.1016/j.tet.2007.11.056 | unige:32 | Abstract | Article HTML | Article PDF
Two new ethynylbipyridine-linked mono- and bis-tetrathiafulvalene (TTF) derivatives, together with a Ru(II) complex, were synthesized using Sonogashira coupling reactions and characterized by UV/vis spectroscopy and cyclic voltammetry. They display a clear electrochemically amphoteric behavior consisting of two reversible single-electron oxidation waves (typical for TTF derivatives) and one reversible single-electron reduction wave (bpy) and act as donor–acceptor (D–A) systems. Furthermore, for the Ru(II) complex, a quite intense fluorescence originating from the 3MLCT state is observed.
  • Dual Luminescence and Long-lived Charge Separated states in Donor-Acceptor Assemblies based on Tetrathiafulvalene Fused Ruthenium(II)-Polypyridine Complexes
    C. Leiggener, N. Dupont, S.-X. Liu, C. Goze, S. Decurtins, E. Breitler and A. Hauser
    Chimia, 61 (10) (2007), p621-625
    DOI:10.2533/chimia.2007.621 | unige:3580 | Abstract | Article PDF
The creation of long-lived charge-separated states in donor-acceptor assemblies has been the goal of many studies aimed at mimicking the primary processes in photosynthesis. Here we present such assemblies based on tetrathiafulvalene (TTF) as electron donor and a dipyridophenazine (dppz) unit as electron acceptor in the form of a fused ligand (TTF-dppz) coordinated to ruthenium(II) via the dipyrido coordination site and with 2,2′-bipyridine (bpy) as auxiliary ligand, namely [Ru(bpy)3−x(TTF-dppz)x]2+ (x = 1−3). For x = 2, irradiation into the metal to dppz charge transfer transition results in electron transfer from TTF to ruthenium, thus creating a charge-separated state best described by [(TTF+-dppz)Ru(dppz-TTF)(bpy)]2+ with a lifetime of 2.5 μs in dichloromethane.
  • Photoinduced Energy Transfer Processes within Dyads of Metallophthalocyanines Compactly Fused to a Ruthenium(II) Polypyridine Chromophore
    M. Haas, S.-X. Liu, A. Kahnt, C. Leiggener, D.M. Guldi, A. Hauser and S. Decurtins
    Journal of Organic Chemistry, 72 (20) (2007), p7533-7543
    DOI:10.1021/jo0710477 | unige:3188 | Abstract | Article HTML | Article PDF
An unsymmetric, peripherally octasubstituted phthalocyanine (Pc) 1, which contains a combination of dipyrido[3,2-f:2‘,3‘-h] quinoxaline and 3,5-di-tert-butylphenoxy substituents, has been obtained via a statistical condensation reaction of two corresponding phthalonitriles. Synthetic procedures for the selective metalation of the macrocyclic cavity and the periphery of 1 were developed, leading to the preparation of the key precursor metallophthalocyanines 35 in good yields. Two different strategies were applied to the synthesis of compact dyads MPc−Ru(II) 68 (M = Mg(II), Co(II), Zn(II)). Intramolecular electronic interactions in these dyads were studied by absorption, emission, and transient absorption spectroscopy. Upon photoexcitation, these dyads exhibit efficient intramolecular energy transfer from the Ru(II) chromophore to the MPc moiety.
  • Fused Donor–Acceptor Ligands in RuII Chemistry: Synthesis, Electrochemistry and Spectroscopy of [Ru(bpy)3-n(TTF-dppz)n](PF6)2
    C. Goze, C. Leiggener, S.-X. Liu, L. Sanguinet, E. Levillain, A. Hauser and S. Decurtins
    ChemPhysChem, 8 (2007), p1504-1512
    DOI:10.1002/cphc.200700066 | unige:3192 | Abstract | Article HTML | Article PDF
Three ruthenium(II) polypyridine complexes of general formula [Ru(bpy)3-n(TTF-dppz)n](PF6)2 (n=1-3, bpy=2,2'-bipyridine), with one, two or three redox-active TTF-dppz (4',5'-bis(propylthio)tetrathiafulvenyl[i]dipyrido[3,2-a:2',3'-c]phenazine) ligands, were synthesised and fully characterised. Their electrochemical and photophysical properties are reported together with those of the reference compounds [Ru(bpy)3](PF6)2, [Ru(dppz)3](PF6)2 and [Ru(bpy)2(dppz)](PF6)2 and the free TTF-dppz ligand. All three complexes show intraligand charge-transfer (ILCT) fluorescence of the TTF-dppz ligand. Remarkably, the complex with n=1 exhibits luminescence from the Ru2+dppz metal-to-ligand charge-transfer (3MLCT) state, whereas for the other two complexes, a radiationless pathway via electron transfer from a second TTF-dppz ligand quenches the 3MLCT luminescence. The TTF fragments as electron donors thus induce a ligand-to-ligand charge-separated (LLCS) state of the form TTF-dppz--Ru2+→ -dppz-TTF+. The lifetime of this LLCS state is approximately 2.3 μs, which is four orders of magnitude longer than that of 0.4 ns for the ILCT state, because recombination of charges on two different ligands is substantially slower.
  • An Experimental and Computational Study on Intramolecular Charge Transfer: A Tetrathiafulvalene Fused Dipyridophenazine Molecule
    C. Jia, S.-X. Liu, C. Tanner, C. Leiggener, A. Neels, L. Sanguinet, E. Levillain, S. Leutwyler, A. Hauser and S. Decurtins
    Chemistry - A European Journal, 13 (13) (2007), p3804-3812
    DOI:10.1002/chem.200601561 | unige:3597 | Abstract | Article HTML | Article PDF
To study the electronic interactions in donor-acceptor (D-A) ensembles, D and A fragments are coupled in a single molecule. Specifically, a tetrathiafulvalene (TTF)-fused dipyrido[3,2-a:2',3'-c]phenazine (dppz) compound having inherent redox centers has been synthesized and structurally characterized. Its electronic absorption, fluorescence emission, photoinduced intramolecular charge transfer, and electrochemical behavior have been investigated. The observed electronic properties are explained on the basis of density functional theory.
  • Preparation and characterization of 3-(4,5-ethylenedithio-1,3-dithiol-2-ylidene)naphthopyranone: a luminescent redox-active donor–acceptor compound
    S. Dolder, S.-X. Liu, X. Gugano, M. Atanasov, C.A. Daul, C. Leiggener, A. Hauser, A. Neels and S. Decurtins
    Tetrahedron, 62 (48) (2006), p11106-11111
    DOI:10.1016/j.tet.2006.09.032 | unige:3295 | Abstract | Article HTML | Article PDF
A new 1,3-dithiol-2-ylidene substituted naphthopyranone 2 has been synthesized and characterized. UV–vis spectroscopic and cyclic voltammetry results, interpreted on the basis of density functional theory, show that 2 displays an intramolecular charge-transfer transition and acts like a donor–acceptor (D–A) system. Furthermore, a weak fluorescence originating from the excited charge-transfer state is observed.
  • A redox-active tri star molecule: merging of TTF and HAT chemistry
    C. Jia, S.-X. Liu, C. Tanner, C. Leiggener, L. Sanguinet, E. Levillain, S. Leutwyler, A. Hauser and S. Decurtins
    ChemComm, (17) (2006), p1878-1880
    DOI:10.1039/b601173j | unige:3307 | Abstract | Article HTML | Article PDF
A planar π-conjugated heteroaromatic molecule 1 has been synthesized and fully characterized; it combines two characteristics, a charge-transfer transition originating from its inherent donor–acceptor nature in its neutral state and an intervalence charge-transfer transition in its 12+ mixed-valence state.
  • Inter- and Intramolecular Interactions in Some Supramolecular Photochemical Systems
    S. Delahaye, C. Loosli, S.-X. Liu, S. Decurtins, G. Labat, A. Neels, A. Loosli, T.R. Ward and A. Hauser
    Advanced Functional Materials, 16 (2) (2006), p286-295
    DOI:10.1002/adfm.200500329 | unige:3286 | Abstract | Article PDF
In supramolecular systems, the interaction between different units modulates their photophysical properties. a) For platinum(II) complexes with ligands that have extended π systems, π-stacking and direct metal-metal interactions result in the formation of excimers with characteristically red-shifted luminescence. Time-resolved emission spectra show clear evidence of dual luminescence. b) In phthalocyanines to which electron-donating tetrathiafulvalene (TTF) groups have been fused, the luminescence is strongly quenched by intramolecular electron transfer. The luminescence can be switched on by oxidation of the TTF groups. c) The luminescence of ruthenium tris-bipyridyl derivatives is strongly influenced by the environment. Linked to biotin, the luminescence quantum yield of such a complex is enhanced by 30 % upon binding to avidin. Furthermore, the binding to avidin induces a circular-dichroism signal from the π-π* transition of the initially racemic ruthenium tris-bipyridyl derivative.
  • Synthesis and Electrochemical and Photophysical Studies of Tetrathiafulvalene-Annulated Phthalocyanines
    C. Loosli, C. Jia, S.-X. Liu, M. Haas, M. Dias, E. Levillain, A. Neels, G. Labat, A. Hauser and S. Decurtins
    Journal of Organic Chemistry, 70 (13) (2005), p4988-4992
    DOI:10.1021/jo0501801 | unige:3274 | Abstract | Article HTML | Article PDF
The synthesis of tetrakis(tetrathiafulvalene)-annulated metal-free and metallophthalocyanines 58 via the tetramerization of the phthalonitrile derivative 4 is reported. All of them have been fully characterized by electronic absorption spectroscopy, thin-layer cyclic voltammetry, mass spectrometry, and elemental analysis. Their solution electrochemical data show two reversible four-electron oxidation waves, indicating that these fused systems are strong π-electron donors, which give rise to tetra- or octaradical cation species. For the metal-free phthalocyanine 5, additionally a reversible one-electron wave was found in the negative direction arising from the reduction of the macrocycle. Moreover, the tetrathiafulvalene unit acts as an efficient reductive electron-transfer quencher for the phthalocyanine emission, but upon its oxidation, an intense luminescence is switched on.



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