Massimo Boiocchi

University of Pavia, Ticinum, Lombardy, Italy

Are you Massimo Boiocchi?

Claim your profile

Publications (95)344.05 Total impact

  • Athos Maria Callegari, Massimo Boiocchi
    [Show abstract] [Hide abstract]
    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.
    Neues Jahrbuch für Mineralogie - Abhandlungen 01/2015; 192(1). DOI:10.1127/njma/2014/0269 · 0.86 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    Inorganic Chemistry 12/2014; 54(1). DOI:10.1021/ic501527k · 4.79 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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+.
    Chemistry - A European Journal 09/2014; 20(38). DOI:10.1002/chem.201403969 · 5.70 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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.
    Mineralogical Magazine 08/2014; 78(4). DOI:10.1180/minmag.2014.078.4.07 · 1.90 Impact Factor
  • Canadian Journal of Chemistry 08/2014; 92(8):794-802. DOI:10.1139/cjc-2014-0078 · 1.01 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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.
    Dalton Transactions 06/2014; 43(29). DOI:10.1039/c4dt00886c · 4.10 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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.
    Chemical Science 01/2014; 5(5). DOI:10.1039/c3sc53504e · 8.60 Impact Factor
  • Massimo Boiocchi, Luigi Fabbrizzi
    [Show abstract] [Hide abstract]
    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.
    Chemical Society Reviews 01/2014; 43(6). DOI:10.1039/c3cs60428d · 30.43 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
  • Source
  • [Show abstract] [Hide abstract]
    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.
    Inorganic Chemistry 09/2013; 52(18). DOI:10.1021/ic401684u · 4.79 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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).
  • Source
    [Show abstract] [Hide abstract]
    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.
    08/2013; 69(Pt 4):362-70. DOI:10.1107/S2052519213016989
  • [Show abstract] [Hide abstract]
    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(-).
    Inorganic Chemistry 04/2013; 52(9). DOI:10.1021/ic400196a · 4.79 Impact Factor
  • [Show abstract] [Hide abstract]
    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-.
    Journal of the American Chemical Society 04/2013; 135(16). DOI:10.1021/ja4019786 · 11.44 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Asymmetric reactions involving (E)-3-aryl-1-(pyridin-2-yl-N-oxide)prop-2-en-1-ones and cyclic enol silyl ethers show good yields and excellent enantioselectivities (up to 99.9 % ee) when catalysed by bis(oxazoline)-Cu(II) complexes. Different reaction pathways can be followed by different enol silyl ethers: with 2-(trimethylsilyloxy)furan, a Mukaiyama-Michael adduct is obtained, whereas a hetero Diels-Alder cycloadduct was formed by using (1,2-dihydronaphthalen-4-yloxy)trimethylsilane. In the latter reaction, the absolute configuration of the product is consistent with a reagent approach to the less hindered Re face of the coordinated substrate in the reactive complex.
    Chemistry - A European Journal 09/2012; 18(37):11662-8. DOI:10.1002/chem.201201214 · 5.70 Impact Factor
  • M. Zema, M. Boiocchi, R. Oberti
    Acta Crystallographica Section A Foundations of Crystallography 08/2012; 68(a1):s202-s202. DOI:10.1107/S0108767312096092 · 2.07 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: he affinity of azacryptands towards perrhenate has been investigated by potentiometric, 1H NMR spectroscopic and ITC studies in aqueous solutions. The association constants could only be determined for the p-xylyl and m-xylyl azacryptands in the hexaprotonated form. The experimental results showed the outstanding affinity of the p-xylyl cryptand for perrhenate, attributable to the geometric complementarity between the anion and the cavity of the receptor. Single crystals of the inclusion complex could also be obtained. The X-ray diffraction studies indicate that the perrhenate anion is included in the cavity of the receptor and interacts with the ammonium groups by means of both direct and water-mediated H-bonding interactions. The receptors were also investigated in the presence of different anions (i.e. chloride, bromide, iodide, perchlorate and nitrate). The affinity trend demonstrates that the p-xylyl cryptand cavity is more suitable to host large anionic guests such as perrhenate, perchlorate and iodide, despite their low density charge. On the contrary, nitrate, bromide and chloride fit better into the smaller cavity of the m-xylyl cryptand. The higher affinity of the m-xylyl cage towards chloride over that of perrhenate was also demonstrated by the crystal structure of the 1:1 adduct.
    European Journal of Inorganic Chemistry 07/2012; 2012(21):3410–3417. DOI:10.1002/ejic.201200334 · 2.97 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The symmetry and crystal chemistry of a(OH,F)-rich spessartine from Junzico Xijang, Wushan Spessartine Mine, Yunxiao Co., Fujian Province, P.R. China, with composition (X)(Mn2.872+Fe0.092+Ca0.04) (Y)(Al-1.Fe-94(0.06)3+) (Z)[(SiO4)(2.52) (OH1.11F0.81)] have been studied by single-crystal X-ray structure refinement and FTIR spectroscopy. This sample is tetragonal, space group I4(1)/acd, with a = b = 11.6347(3) angstrom, c = 11.6449(3) angstrom, c/a = 1.006, R-all 3.1% (theta(max) = 55 degrees). The two independent tetrahedra differ significantly both in terms of refined bond-lengths and site-scattering values, the latter allowing to confirm the extent of the (OH,F) substitution and to its preferential ordering at O3, the site occupied by the anions coordinated to Z2. FTIR spectra consist of a prominent peak at 3580 cm(-1) and a doublet at 3622-3632 cm(-1). Pleochroic curves suggest assignment to a unique O-H dipole, involved in two different hydrogen bonds (O3-H center dot center dot center dot O2 and O3-H center dot center dot center dot O3, the latter showing two different, O-H center dot center dot center dot H and O-H center dot center dot center dot F, configurations). The observed space group and composition imply: (a) that lowering in symmetry is related to the presence of (OH,F)(4) groups; (b) the existence of a new hydrogarnet end-member with ideal composition (Mn3Al2Z)-Mn-X-Al-Y[(SiO4)(2)(OH)(4)] and significant F content, the first related to the pyralspite series; the sample of this work is close to its 50 : 50 solid solution with spessartine. Geometric considerations and the very limited increase in volume with respect to spessartine suggest that the presence of F is a requisite for the incorporation of significant amount of monovalent anions in pyralspites.
    07/2012; 227(7):385-395. DOI:10.1524/zkri.2012.1487
  • [Show abstract] [Hide abstract]
    ABSTRACT: The complex between scandium triflate and pybox is a good enantioselective catalyst for the reaction between methyl (E)-4-aryl-2-oxo-3-butenoates (1) and enol silyl ethers (2). The main products with (4′S)-isopropyl-, (4′S)-phenyl-, and (4′S,5′S)-4-TIPS-pybox are methyl (4S,4aS,8aS)-4-aryl-8a-trialkylsiloxy-hexahydro-4H-chromen-2-carboxylates (7), which are obtained in good yield and enantioselectivities of more than 95 % ee. Because the reaction gives products with a trans ring junction that cannot derive from a conventional concerted hetero-Diels–Alder pathway, the mechanism involved in the enantioselective catalytic cycle and the origin of the stereoinduction were investigated. The structures of two desilylated products, 8b and 9b, were determined by X-ray crystal analysis. Their absolute configuration was then related to that of 7 by stereospecific isomerization and/or desilylation reactions. If aryl-butenoates 1 are coordinated to the catalyst, forming reacting complexes characterized by the five-membered structure 11, these rigid reacting intermediates give a face discrimination that is determined by the configuration of the pybox 4′-substituent. The resulting face-selective attack of enol silyl ethers to coordinated 1 gives an enantioselective tandem Mukaiyama–Michael addition/intramolecular ring closure reaction, which is an enantioselective formal hetero-Diels–Alder reaction, which rationalizes the absolute configuration of the reaction products.
    European Journal of Organic Chemistry 05/2012; 2012(15). DOI:10.1002/ejoc.201200056 · 3.15 Impact Factor