259 research outputs found
Correction: The reaction of acetonitrile with hydrogen peroxide in alkaline medium: a DFT mechanistic study of green production of amides
No full textCorrection for 'The reaction of acetonitrile with hydrogen peroxide in alkaline medium: a DFT mechanistic study of green production of amides' by Girolamo Casella et al., Phys. Chem. Chem. Phys., 2023, https://doi.org/10.1039/d3cp02024j
Viologen-based ionic liquid crystals: induction of a smectic A phase by dimerisation
No full textThe stability of thermotropic ionic liquid crystals is essentially due
to micro-phase segregation between the ionic heads and the long
alkyl chains. Here we show, using newly synthesized viologen
dimers, that the structure of the central core is another key parameter
to play with in order to tune the mesomorphic behaviour
A DFT study of the vicinal 3J(119Sn,13C) and 3J(119Sn,1H) coupling constants in trimethyl- and chlorodimethylstannyl propanoates
No full textWe have tested the performance of DFT protocols, both at the Scalar relativistic ZORA and non-relativistic
level of theory, for the calculation of the 3J(119Sn,13C) and 3J(119Sn,1H) vicinal couplings for a series of
flexible organotin(IV) derivatives with formula XMe2SnCHRCHR0COOMe (X 1⁄4 Me, Cl; R, R0 1⁄4 Me, Ph). A
satisfactory agreement between experimental and calculated vicinal couplings has been obtained by
taking into account the conformational behaviour of the compounds investigated. The protocols used,
mainly the relativistic one, were found to give a correct picture of the populations and a sufficiently high
overall performance in calculating the vicinal couplings, thereby overcoming the use of empirical
Karplus-type relationships to infer geometrical parameters from 3J(119Sn,13C) and 3J(119Sn,1H)
Spectroscopic signatures of the carbon buckyonions C60@C180 and C60@C240: a dispersion-corrected DFT study
No full textWe have investigated, using dispersion corrected DFT methods, the structure and the spectroscopic properties of carbon buckyonions C60@C180 and C60@C240. C60, C180 and C240 showed a noticeable variation of their geometries in C60@C180 and C60@C240, upon encapsulation. Inclusion of the dispersion correction term in the calculations has a significant effect on the geometry. C60@C180 has a large positive interaction energy, while for C60@C240 a negative value is found indicating that only C240 can easily accommodate C60.
In both cases dispersion interactions strongly contribute to the stabilization of the complexes. Vibrational
frequencies, electronic transitions and NMR properties have been computed. The results show that
encapsulation leads to appreciable variation in the characteristic resonances thus offering a useful tool
for a spectroscopic identification of these species
From Salamanca to Florence: the collection of books and manuscripts of Girolamo da Sommaia (early 17th century)
No full textWith this essay, I intend to reflect on the formation of a patrimony of literary, theatrical, historical, political, and topical writings that traversed from Salamanca to Florence and that, in the course of its journey, changed and acquired a physiognomy that took shape in successive stages. The creator, Girolamo da Sommaia, took care of the collection of these writings throughout his entire life. Coming from a family with an excellent economic standing and linked through his mother Margherita to the Guicciardini family of Florence, descendants of the historian and politician Francesco, Girolamo obtained a licence to study outside the Medici Grand Duchy in his early years. Wishing perhaps to broaden the horizons of his education and his travel and life experiences, he received permission to follow law courses at the University of Salamanca, the most influential in the Spanish monarchy.
During the eight years he spent in Salamanca (from 1599 to 1607), Sommaia amassed a significant collection of printed books, manuscripts, and loose sheets. These covered a broad thematic and typological spectrum, ranging from history to theatre, poetry to prose, and reports to gazettes. In his move from Castile to Tuscany, he transported a large number of writings, both printed and manuscript, loose sheets, and bound manuscripts, which, after finding their way into the ancient collections of the Florentine libraries, today represent one of the most important core collections of Spanish volumes, manuscripts, and documents preserved Florence. In this essay, I will focus on the selection and collection of these materials, the forms of reproduction of the writings through copies, the creation of miscellaneous collections, the sorting procedures, and the phase of selecting the texts to be brought to Florence. Within the briefly traced biographical profile of Sommaia, two phases are to be considered: the first covers part of the years Girolamo spent in Salamanca, during which he collected large quantities of books and manuscripts; the second, much shorter, corresponds to his move to Tuscany and the choices related to the selection of the papers and books to be taken with him
DFT study of the interaction free energy of p–p complexes of fullerenes with buckybowls and viologen dimers
No full textWe present a theoretical investigation, by means of DFT protocols, of the complexation
thermodynamics of (i) complexes of C70 and C60 fullerenes with bowl-shaped hexabenzocoronene
derivatives and (ii) complexes of C60 with viologen dimers. The recent functionals of the M06
family, accounting for p–p interactions to a good level of approximation, have been used to
calculate the interaction free energies. For the former complexes, the good agreement between the
calculated results and the experimental data confirms the reliability of the protocol used. On these
grounds, we then checked the stability of a series of complexes of C60 with some viologen dimers,
1BPnBP1 (n = 6–9), where two N-methylated bipyridinium units are linked by an alkyl chain of
variable length, acting as molecular tweezers. Both forms of the viologen cores, that is the cation
(each core doubly charged) and the reduced neutral form, were considered. For a suitable chain
length a free energy gain upon complexation is predicted for the neutral form while the
complexation of C60 by the cationic form is disfavoured mainly for entropic reasons
Recent Results of Studies on Dialkyltin(IV) Complexes of Acidic Derivatives of Carbohydrates
No full textIonic liquid crystals based on viologen dimers: tuning the mesomorphism by varying the conformational freedom of the ionic layer
No full textWe investigated the liquid crystal behaviour of newly synthesised bistriflimide salts of symmetric viologen dimers. A smectic A phase was observed for intermediate spacer lengths and for relatively long lateral alkyl chains. The systems were characterised by thermal analysis, polarised optical microscopy, X-ray scattering and solid-state NMR. An intermediate ordered smectic phase was also exhibited by the compounds (except for systems with very short lateral chains) consisting of molten layers of alkyl chains and partially ordered ionic layers. These results, relating to the mesomorphic behaviour of viologen salts, are qualitatively compared to those of the more common imidazolium salts, highlighting the importance of the conformational degrees of freedom of the anions and of the cationic core. It appears that fine tuning of the conformational degrees of freedom of the ionic layer is an important component of mesophase stabilisation
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