Massimo Boiocchi

University of Pavia, Ticinum, Lombardy, Italy

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Publications (104)367.11 Total impact

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    ABSTRACT: The three nitrophenyl-cyclam derivatives (nitrocyclams): 1-(4-nitrophenyl)-1,4,8,11-tetraazacyclotetradecane (2), 1-(2-nitrophenyl)-1,4,8,11-tetraazacyclotetradecane (3), and 1-(2,4-dinitrophenyl)-1,4,8,11-tetraazacyclotetradecane (4), in an MeCN solution, specifically incorporate the Cu(II) ion according to an irreversible process signaled by disappearance of the yellow color for a concentration c < 1 × 10(-4) M and by a yellow-to-red color change for c ≥ 1 × 10(-3), and must be considered efficient and specific dosimeters of copper(II) salts. When present in the ortho position of the nitrophenyl substituent, the -NO2 group coordinates the Cu(II) according to a scorpionate mode, while the metallocyclam system exhibits a trans-I configuration. In an MeCN solution the red trans-I-[Cu(II)(3)](2+) and trans-I-[Cu(II)(4)](2+) scorpionate complexes slowly convert into the violet trans-III scorpionate complexes. Kinetic aspects of the trans-I-to-trans-III configurational rearrangement were investigated in detail for the [Cu(II)(4)](2+) system. In particular, the conversion is spectacularly accelerated by catalytic amounts of Cl(-), NCO(-), and F(-). While for Cl(-) and NCO(-) the effect can be associated with the capability of the anion to stabilize through coordination a possible dissociative intermediate, the amazingly powerful effect of F(-) must be related to the preliminary deprotonation of one N-H fragment of the macrocycle, driven by the formation of the HF2(-) ion. Most of the metal complex species studied in solution were isolated in a crystalline form, and their molecular structures were elucidated through X-ray diffraction studies. This study documents the first examples of effective metal coordination by the nitro group.
    No preview · Article · Oct 2015 · Inorganic Chemistry
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    ABSTRACT: The crystal-chemical characterization of an amphibole with an unusual composition, A(Na0.76K0.24)B(Ca1.42Na0.56Mn2+0.02)C(Mg2.64Fe2+1.95Mn2+0.07Mg2.64Zn0.01Fe3+0.01Ti4+0.32)T(Si7.18Al0.82)O22W[(OH)0.58O0.27F1.15], found in pegmatitic veins at Kariåsen, Larvik Plutonic Complex, Norway, provides an excellent example of the detection and estimation of the oxo component in amphibole. The use of Ti as a proxy for the oxo component is discussed and a procedure to derive accurate Ti partitioning from the results of structure refinement is described. Because the presence and amount of oxo component in amphiboles are important in order to determine values of ƒO2 and ƒH2O, especially in igneous and magmatic systems, this procedure should be applied any time the compositional data or the petrological context indicate the presence of significant Ti, or suggest that the oxo component may be a relevant issue.
    Full-text · Article · Oct 2015 · The Canadian Mineralogist
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    ABSTRACT: Following the characterization of the new amphibole species fluoro-leakeite, ideally ANa BNa2 C(Mg2Al2Li) TSi8 O22 WF2, at Norra Kärr (Sweden), so far considered the type locality of eckermannite, re-examination of the holotype material of eckermannite deposited at the Museum of Natural History in London (BM 1949.151) and of the original sample analyzed by Törnebohm (1906) confirmed that they both are actually fluoro-leakeite. A survey of literature data showed that the only analysis reported for eckermannite is that of sample AMNH 108401 from the Jade Mine Tract, Myanmar. Complete characterization of that sample has led to the approval of a new holotype for eckermannite (IMA-CNMNC 2013-136), ideally ANa BNa2 C(Mg4Al) TSi8 O22 W(OH)2, which is described in this work. Holotype eckermannite from Myanmar has the empirical unit formula A(Na0.87K0.06)∑=0.93 B(Na1.89Ca0.11)∑=2.00 C(Mg3.87Fe2+0.09Mn0.01Fe3+0.38Al0.62)∑=4.97 TSi8.00 O22 W(F0.03OH1.97)∑=2.00. It is monoclinic, C2/m, with a = 9.8087(7), b = 17.8448(13), c = 5.2905(4) Å, β = 103.660(1), V = 899.8(1) Å3; Z = 2, Dcalc = 3.02 g/cm3. Optics: biaxial (−); α = 1.605, β = 1.630, γ = 1.634 all ±0.002 (λ = 590 nm). The 10 strongest reflections in the X-ray powder pattern [d values (in Å), I, (hkl)] are: 2.702, 100, [(3̄31) (151)]; 3.395, 59, (131); 3.128, 56, (310); 2.525, 56, (2̄02); 8.407, 42, (110); 2.574, 36, [(061) (002)]; 3.257, 34, (240); 2.161, 33, (261); 2.966, 33, (060); 4.460, 30, (040). The reason for the rarity of eckermannite compositions are examined and discussed based on considerations on the short-range order of A cations and W anions.
    Full-text · Article · Apr 2015 · American Mineralogist
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    ABSTRACT: Magnesio-arfvedsonite, the CFe3+-dominant analogue of eckermannite, has been found in a sample of “szechenyite” in the mineral collection of the American Museum of Natural History (AMNH H35024). It comes from the northern part of the Jade Mine Tract near Hpakan, Kachin State, Myanmar. Associated minerals are kosmochlor–jadeite solid-solution pyroxene and clinochlore. The ideal formula of magnesio-arfvedsonite is ANaBNa2C(Mg4Fe3+)TSi8O22W(OH)2, and the empirical formula derived from electron microprobe analysis and single-crystal structure refinement for the sample of this work is A(Na0.96K0.04)Σ=1.00B(Na1.57Ca0.40Fe2+0.02Mn0.01)Σ=2.00C(Mg4.26Fe2+0.19Fe3+0.41Al0.11Ti4+0.03)Σ=5.00T(Si7.99Al0.01)Σ=8.00O22W[F0.02(OH)1.98]Σ=2.00. The unit-cell dimensions are a = 9.867(1), b = 17.928(2), c = 5.284(1) Å, β = 103.80(2)°, V = 907.7 (2) Å3, Z = 2. Magnesio-arfvedsonite is biaxial (–), with α = 1.624, β = 1.636, γ = 1.637, all ± 0.002 and 2Vobs = 36(1)°, 2Vcalc = 32°. The ten strongest reflections in the X-ray powder pattern [d values (in Å), I, (hkl)] are: 2.708, 100, (151); 3.399, 68, (131); 3.144, 63, (310); 2.526, 60, (202); 8.451, 46, (110); 3.273, 39, (240); 2.167, 37, (261); 2.582, 34, (061); 2.970, 34, (221); 2.326, 33, [(251) (421)].
    Full-text · Article · Apr 2015 · Mineralogical Magazine
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    ABSTRACT: Katophorite has the ideal formula ANaB(NaCa)C(Mg4Al)T(Si7Al)O22W(OH)2 (Hawthorne et al., 2012). No published analyses of amphiboles fall in the katophorite compositional field, except that of Harlow and Olds (1987) for an amphibole from near Hpakan in the Jade Mine Tract, Myanmar. This amphibole was approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (vote 2013-140) as katophorite, and is reported here. Holotype katophorite is monoclinic, space group C2/m, a = 9.8573(8), b = 17.9617(15), c = 5.2833(4) Å, β = 104.707(2)°, V = 904.78(13) Å3, Z = 2. The calculated density is 3.091 g cm–3. In plane-polarized light, katophorite is pleochroic, X = pale blue (medium), Y = light blue-green (strongest), Z = colourless; X ∧a = 30.6° (β obtuse), Y || b, Z ∧c = 15.8 (β acute). It is biaxial negative, α = 1.638, β = 1.642, γ = 1.644, all ± 0.002; 2Vobs = 73(1)°, 2Vcalc = 70°. The eight strongest lines in the powder X-ray diffraction pattern are [d in Å (I)(hkl)]: 2.700 (100)(151), 3.129 (69)(310), 2.536 (65)(202), 3.378 (61)(131), 8.421 (55)(110), 2.583 (46)(061), 2.942 (43)(221) and 2.334 (41)(351). Electron-microprobe analysis of the refined crystal gave SiO251.74, Al2O37.38, TiO2 0.14, FeO 1.55, Fe2O3 2.82, MgO 18.09, CaO 8.17, Na2O 6.02, K2O 0.24, F 0.06, H2Ocalc. 1.80, Li2Ocalc. 0.09, sum 100.55 wt.% (Li2O and H2O based on the results of single-crystal structure refinement). The formula unit, calculated on the basis of 24 (O,OH,F) with (OH + F + O) = 2 is: A(Na0.85K0.04)Σ=0.89B(Ca1.22Na0.78)Σ=2.00C(Mg3.76Al0.43Fe3+0.30Cr3+0.27Fe2+0.18Li0.05Ti4+0.01)Σ=5.00T(Si7.21Al0.79)Σ=8.00O22W[(OH)1.67O0.30F0.03)]Σ=2.00.
    Full-text · Article · Apr 2015 · Mineralogical Magazine
  • Athos Maria Callegari · Massimo Boiocchi
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    ABSTRACT: The crystal structure and crystal-chemical features of häggite: V+3V4+O2(OH)3; have been confirmed on the basis of new X-ray diffraction data collected on a small single crystal from Gambatesa mine (Italy). The crystal structure of häggite is monoclinic, C2/m space group, with a = 12.2203(21), b = 2.9991(5), c = 4.8334(9) Å; β = 98.384(4)°, V = 175.25(5) ų, Z = 2. The crystal structure contains one independent V octahedron populated by V3+ and V4+ and the final bond valence analysis confirms the crystal-chemical formula of natural häggite : [V](V3+V4+)2[O1]O2–[O2](OH)2[O3](O2–OH)2. Only the O1 atom site, shared between two octahedra, shows an anomalously low incident-bond valence sums (1.72 valence units). The possible hydrogen bond motif in presence of 3 OH groups imposes the use of half populated H sites, which cannot be observed in the final ΔF map. The refinement of the complete structural model converges to a final R obs of 0.039 for 244 reflection with IO > 3 σ(IO). The crystallographic data obtained in our natural sample have been compared with those of häggite from the type locality and with a synthetic phase named “haggite” and described as V4+2O3(OH)2.
    No preview · Article · Jan 2015 · Neues Jahrbuch für Mineralogie - Abhandlungen
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    ABSTRACT: The novel macrocyclic copper(II) complexes [2](2+) and [3](2+), carrying one or two (nitrophenyl)urea fragments appended to an azacyclam or diazacyclam framework, exploit the hydrogen-bond-forming abilities of the urea subunits, along with the metal-ligand interaction, in the recognition of anionic species. Equilibrium studies in acetonitrile performed on [2](2+) and [3](2+) show that (nitrophenyl)urea pendant arms strongly interact with anionic species such as carboxylates and phosphates, which display both coordinating tendencies toward copper(II) and good affinity toward urea subunits. Stability constants of the adducts are considerably higher than those determined for the interaction of the same anions with a "plain urea" reference compound, confirming the synergistic action of metallomacrocyclic and urea subunits. Complex [2](2+) forms 1:1 adducts with acetate, benzoate, hydrogendiphosphate, and dihydrogen phosphate, while complex [3](2+) interacts with the same anions according to both 1:1 and 1:2 stoichiometries, with the exception of hydrogendiphosphate, which forms only the 1:1 adduct with a distinctly high association constant (log K > 7). Spectrophotometric investigations suggest that oxoanionic species interact with the complexes according to a "bridged" mode, inducing the macrocyclic systems to adopt a scorpionate-like conformation, as confirmed by crystallographic studies on the [3](2+)/succinate adduct.
    No preview · Article · Dec 2014 · Inorganic Chemistry
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    ABSTRACT: From an EtOH/H2O solution, 0.3 M each of Ni2+ and cyclic triamine tacn (2; tacn=1,4,7-triazacyclononane), after 10 min refluxing and cooling at room temperature, copious and comparable amounts of blue crystals (containing the complex [Ni(tacn)(H2O)3]2+) and pink crystals (containing in the same cell both [Ni(H2O)6]2+ and [Ni(tacn)2]2+) precipitated. This unusual behaviour is ascribed to the fact that at the refluxing temperature the three species are present at the equilibrium in similar concentrations, which are frozen on cooling, due to the inertness of the macrocyclic complexes [Ni(tacn)(H2O)3]2+ and [Ni(tacn)2]2+.
    Full-text · Article · Sep 2014 · Chemistry - A European Journal
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    ABSTRACT: A second occurrence of ferri-fluoro-leakeite has been identified in the Bratthagen nepheline syenite pegmatite (Vestfold County, Norway). With respect to the holotype found at the Verkhnee Espe deposit (Akjailyautas Mountains, Kazakhstan; Cámara et al., 2010), it is closer to the ideal composition because of its larger Li and Mg contents and the absence of an oxo-component; however, it has a significant Zn content (0.29 a.p.f.u.). The ideal formula of ferri-fluoro-leakeite is ANaBNa2C(Mg2Fe3+2Li)TSi8O22WF2 and the empirical formula derived from electron-microprobe analysis and single-crystal structure refinement for the sample used here is A(Na0.68K0.32)Σ=1.00BNa2.00C(Mg1.69Mn2+0.25Fe2+0.24Zn 0.29Al0.23Fe3+1.50Ti0.02Li0.78)Σ=5.00TSi8O22W(F1.59(OH)0.41)Σ=2.00. Unitcell data are a = 9.788(2), b = 17.826(3), c = 5.282(1) Å, β = 104.195(5)°, V = 893.5 (3) Å3, Z = 2. Crystal-chemical analysis shows that Li is ordered at the M(3) site and Zn is ordered mainly at the M(2) site, confirming previous findings for Li-bearing amphiboles. The new data also make quantification of the oxo component in Na amphiboles possible.
    Full-text · Article · Aug 2014 · Mineralogical Magazine
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    ABSTRACT: The two coordinatively unsaturated complexes [Cu(cyclam)]2+ (cyclam: 1,4,8,11-tetraazacyclotetradecane, 1) and [Cu(Bn4cyclam)] 2+ (Bn4cyclam: 1,4,8,11-tetrabenzyl-1,4,8,11- tetraazacyclotetradecane, 2) in an MeCN solution uptake an anion X- (halide, pseudohalide) to give square pyramidal ternary complexes, whose stability has been determined through spectrophotometric titration experiments. The formation of a five-cordinate complex is favored by the trans-I configuration of the [Cu(Bn4cyclam)]2+ receptor, but it is contrasted by the severe steric repulsions exerted by the benzyl substituents on the macrocyclic framework. No significant repulsive effects have been observed in anion binding to the [Cu(cyclam)]2+ receptor, exhibiting a trans-III configuration. The existence of a linear relationship between the magnitude of the red shift experienced by the d-d absorption band on anion binding and log K values is discussed.
    No preview · Article · Aug 2014 · Canadian Journal of Chemistry
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    ABSTRACT: In this work, we report on two new asymmetric dicopper cryptates, characterized by alternate furanyl and p-xylyl spacers. The results of the potentiometric, UV-vis and X-ray diffraction studies are discussed. In particular, for one of the cages in the octaprotonated form, the crystal structure of the complex with nitrate is described. From the point of view of the anion binding in water, the new dicopper cryptates display stronger similarities to each other than to the symmetric analogues (i.e. p-xylyl and furan cryptates). The substitution of even only one spacer modifies the distance between the metal ions. This prevents the development of the CT band, typically accompanying the binding of halides by the furan cryptate, and favors the formation of complexes of different stoichiometry with the linear azide anion, not observed for the symmetric cryptates. The obtained results may be very helpful in the design of new molecular receptors based on dimetallic cryptates, in particular for the tuning of the sensitivity towards specific anionic substrates.
    Full-text · Article · Jun 2014 · Dalton Transactions
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    ABSTRACT: The selective binding of 99 Tc pertechnetate (99 TcO 4 À) in water is a big challenge. Recently, our group reported on the p-xylyl aza-cryptand, as the first molecular receptor for 99 TcO 4 À in aqueous solution. Here, we show that the introduction of a fluorescent unit in the azacryptand's framework leads to a new molecular system, able to selectively recognize and sense the pertechnetate anion at mM concentration. In water at pH 2, where the cage is in the hexaprotonated form, pertechnetate recognition is signalled by the quenching of the receptor's emission. Noticeably, environmentally ubiquitous anions, such as chloride, nitrate and sulfate do not interfere in the sensing, as they have no effect on our chemo-sensor's fluorescence. These unprecedented results are promising for the development of simple and smart devices for the recovery of 99 TcO 4 À from contaminated aqueous solutions.
    Full-text · Article · Jan 2014 · Chemical Science
  • Massimo Boiocchi · Luigi Fabbrizzi
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    ABSTRACT: In the presence of d(10) metal ions, prone to tetrahedral coordination, ligands containing two bidentate subunits will give rise to double-stranded helical complexes (helicates). Upon electrochemical oxidation of Cu(I) to Cu(II), the helicate complex tends to disassemble, thus giving rise to two mononuclear Cu(II) complexes with tetragonal geometry. Upon subsequent Cu(II)-to-Cu(I) electrochemical reduction, two Cu(I) complexes instantaneously re-assemble to give the helicate complex. A helicand containing a chiral subunit (e.g. 1,2-substituted cyclohexanediamine) contains a racemic mixture of the R,R and S,S enantiomers. The racemic helicand, reacting with Cu(I), forms dimetallic helicates, in which the two strands show the same chirality, whether R,R or S,S, thus obeying the principle of homochiral recognition.
    No preview · Article · Jan 2014 · Chemical Society Reviews
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    ABSTRACT: accurate analytical investigations have led to a more complete mineralogical framework of the ancient places at Fosso Mandromicci where minerals were found. Desire of the authors is to update and expand the article published earlier on this journal with a general mineralogical list of the locality not devoid of surprises and interesting finds including arsentsumebite, aurichalcite, beaverite-(Cu), chlorargyrite, corkite, mimetite, oxyplumboroméite, pyrolusite, pyromorphite, tsumebite, willemite and silver in samples that can be considered “historic” for Tuscany. A brief note describing the locality will introduce the minerals sampled, visually recognized and/or certified by SEM-EDS studies, Raman and diffraction. Arsentsumebite and tsumebite represent, respectively, the first and second occurrence for Italy.
    No preview · Article · Dec 2013
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    Full-text · Dataset · Nov 2013
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    ABSTRACT: The bis-bidentate ligand, obtained from Schiff base condensation of RR-1,2-cyclohexanediamine and 8-naphthylmethoxyquinoline-2-carbaldehyde (L-L), forms with [Cu(I)(MeCN)4]ClO4 a double strand helicate complex, made especially stable by the presence of four definite interstrand π-π interactions involving a quinoline subunit and a naphthylmethoxy substituent of the two strands. The [Cu(I)2(L-L)2](2+) complex, which does not decompose even on excess addition of either L-L or Cu(I), undergoes a two electron oxidation in MeCN, through two one-electron fully reversible steps, separated by 260 mV, as shown by cyclic voltammetry (CV) studies. The high stability of the mixed valence complex [Cu(I)Cu(II)(L-L)2](3+) with respect to disproportionation to [Cu(I)2(L-L)2](2+) and [Cu(II)2(L-L)2](4+) is essentially due to a favorable electrostatic term. Cu(II) forms with L-L a stable species, with a 1:1 stoichiometric ratio, but, in the absence of crystallographic data, it was impossible to assess whether it is of mono- or dinuclear nature. However, CV studies on an MeCN solution containing equimolar amounts of Cu(II) and L-L showed the presence in the reduction scan of two fully reversible waves, separated by about 250 mV, which indicated the presence in solution of a dicopper(II) double strand helicate complex, [Cu(II)2(L-L)2](4+). This work demonstrates that additional interstrand π-π interactions can favor the formation of unusually stable dicopper(I) and dicopper(II) helicate complexes.
    Full-text · Article · Sep 2013 · Inorganic Chemistry
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    ABSTRACT: This short note reports the first occurrence in Italy of studtite, [(UO2)O2(H2O)2]•2H2O, which was found during a search on the dumps of the uranium mine of Novazza, Valgoglio, Bergamo, Lombardy. The identification was carried out at the Department of Earth and Environmental Sciences of the University of Pavia by powder X-ray diffraction (PXRD).
    Full-text · Article · Sep 2013
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    ABSTRACT: This paper describes the structure and properties of the drug domperidone and a novel 1:1 domperidone succinate salt. The new salt is characterized by means of thermal, spectroscopic, microscopic and powder diffraction measurements. The crystal structures of the salt and, for the first time, of pure domperidone have been determined by means of single-crystal X-ray diffraction. In both structures, the piperidine ring of domperidone adopts the expected chair conformation, and supramolecular centrosymmetric R2(2)(8) motifs are formed by N-H...O hydrogen bonds between chlorine-substituted oxobenzimidazolyl groups. Further N-H...O hydrogen bonds occur between non-substituted oxobenzimidazolyl groups and the resulting C(4) motifs originates hydrogen-bonded chains, extending along the crystallographic b axis. In the salt, a single N-H...O hydrogen bond forms between the protonated nitrogen of the piperidine ring and the carboxylic O atom of the succinate ion. Two alternative and mutually exclusive positions for the nonsubstituted oxobenzimidazolyl group have also been observed; this disorder makes the hydrogen-bonded chains originating from the bicyclic group polar. The dissolution behaviour of the salt in dosage form is compared with two reference commercial products. The salt shows an increased solubility, a characteristic that could be of great advantage from a pharmaceutical view point.
    Full-text · Article · Aug 2013 · Acta Crystallographica Section B: Structural Science
  • Giorgio Baggi · Massimo Boiocchi · Carlo Ciarrocchi · Luigi Fabbrizzi
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    ABSTRACT: Covalent linking of a Ru(terpy)2(2+) substituent improves recognition and sensing properties of the urea subunit toward anions. Urea's anion affinity is enhanced by the electrostatic attraction exerted by the Ru(II) cation and by the electron-withdrawing effect exerted by the entire polypyridine-metal complex. Such an enhancement of the anion affinity, which results from the combination of a through-space and a through-bond effect, is greater than that exerted by the classical neutral electron-withdrawing substituent nitrophenyl. Small yet significant modifications of π-π* and MLCT bands of the Ru(terpy)2(2+) chromophore, detected through UV-vis spectrophotometric titrations, allowed the determination of the constants for the formation of receptor-anion H-bond complexes in diluted MeCN solution. On (1)H NMR titration experiments, carried out under more concentrated conditions, the interaction of a second Cl(-) ion was observed, taking place through an outer-sphere mechanism. The Ru(terpy)2(2+) substituent favors the deprotonation of a urea N-H fragment on addition of a second equivalent of fluoride, with formation of HF2(-).
    No preview · Article · Apr 2013 · Inorganic Chemistry
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    ABSTRACT: The anion binding tendencies of the two fluorogenic ureas L1H and L2H, containing the 2 anthracenyl and 1 pyrenyl moieties as signaling units, respectively, have been investigated in MeCN and DMSO by absorption, emission and 1H-NMR spectroscopies. The formation of stable 1:1 receptor:anion H bond complexes has been confirmed by structural studies on the crystalline [Bu4N][L1...Cl] and [Bu4N][L2H...CH3COO] salts. Complexation induces significant variations of the emission properties of L1H and L2H according to a multifaceted behavior, which depends upon the fluoro¬genic substituent, the solvent and the basicity of the anion. Poorly basic anions (Cl, Br) cause a red shift of the emission band(s). Carboxylates (CH3COO, C6H5COO) induce fluorescence quenching due to the occurrence of an electron transfer process taking place in the locally excited complex [*L H...X]. However, this excited complex may undergo an intra-complex proton transfer from one urea NH fragment to the anion, to give the tautomeric excited complex [L...HX]*, which emits at higher wavelength, the process being favoured by solvent polarity (DMSO > MeCN) and nature of the fluorogenic substituent (pyrene > anthracene). F displays a unique behavior: it forms with L1H a stable [LH...F], which in the excited state undergoes intra-complex proton transfer, to give the poorly emissive excited tautomer [L...HF]*. With L2H, on moderate addition of F, the 1:1 H bond complex forms and the blue fluorescence of pyrene is quenched. Large excess addition of F promotes deprotonation of the ground state complex, according to the equilibrium [L2H...F] + F- = [L2]- + HF2-. The deprotonated receptor [L2]- is distinctly emissive (yellow fluorescence), which generates the fluorimetric response ON1-OFF-ON2 of receptor L2H with respect to F-.
    No preview · Article · Apr 2013 · Journal of the American Chemical Society