The description of chemical bonding in real space translates the non-local picture provided by quantum mechanics in terms of molecular orbitals into a chemically friendly and easy-to-grasp representation. The latter is based on paths of electron charge density that connect pairs of bonded atoms. Being amenable to experimental determination through accurate X-ray diffraction experiments at low temperature, the charge density picture allows to compare experiment and theory on the same grounds.
In our lab, a Samson closed circle He cryostat is fully operational. It is able to work in the 20 K – RT range of T, allowing a fine and accurate control of the temperature of the crystal thanks to an equilibrated isothermal cavity. The technology was originally developed in 70s at Caltech, Pasadena (USA), and the know–how was brought in Milano by prof. Riccardo Destro, the former group leader (now retired). Collecting diffraction data at extremely low temperature ensures to dampen the atomic thermal motion, and results in a significant (up to 50 %) enhancement of the diffraction data at very high resolution (sinθ/λ > 1.0 Å–1). This is necessary to successfully deconvolute the atomic thermal motion from the static charge density. This way, very accurate experimental charge density distributions can be obtained, which in turn provide us with a sub-nanometer scale magnifying lens on nature and properties of chemical bonds.
An Oxford Cryosystem N2 open flow cryostat is also available to perform faster data collections down to 100 K.
The analysis of the experimental charge density deepens our understanding of intermolecular interactions, giving quantitative hints on how molecules recognize themselves in the crystal structure. In addition, covalent bond networks can be studied and rationalized, deepening our understanding on keystone chemical concepts such as aromaticity and antiaromaticity, electron delocalization, hypervalence, conjugation and coordinative interactions.
Relevant publications:
Book Chapters:
Riccardo Destro, Leonardo Lo Presti, Raffaella Soave, A. E. Goeta, "Multi-temperature charge density studies", invited monography for the book on "Modern Charge Density Analysis", Ed. C. Gatti and P. Macchi, on behalf of Springer Ed. (2010), DOI: 10.1007/978-90-481-3836-4_19; ISBN: 978-90-481-3835-7
Papers:
Riccardo Destro, Mario Barzaghi, Raffaella Soave, Pietro Roversi, Leonardo Lo Presti*: Accurate experimental characterization of the labile N–Cl bond in N-chloro-N′-(p-fluorophenyl)-benzamidine crystal at 17.5 K. CrystEngComm, 2022, 24, 6215-6225, DOI: https://doi.org/10.1039/D2CE00957A
Riccardo Destro*, Pietro Roversi, Mario Barzaghi, Leonardo Lo Presti: Anharmonic Thermal Motion Modelling in the Experimental XRD Charge Density Determination of 1-Methyluracil at T = 23 K. Molecules (MDPI), 2021, 26, 3075, DOI: https://doi.org/10.3390/molecules26113075
Riccardo Destro*, Pietro Roversi, Raffaella Soave, Arjan Hovestad, Leonardo Lo Presti: Experimental Charge Density Analysis and Electrostatic Properties of Crystalline 1,3- Bis(Dimethylamino)Squaraine and Its Dihydrate from Low Temperature (T = 18 and 20 K) XRD Data. Crystals (MDPI), 2020, 10. 894, DOI: 10.3390/cryst10100894
Giovanna Bruno, Giovanni Macetti, Leonardo Lo Presti, Carlo Gatti*: Spin Density Topology. Molecules (MDPI), 2020, 25, 3537, DOI: 10.3390/molecules25153537
Giada Finocchio, Silvia Rizzato, Giovanni Macetti, Gers Tusha, Leonardo Lo Presti*: Unravelling the Chemistry of the [Cu(4,7-Dichloroquinoline)2Br2]2 Dimeric Complex through Structural Analysis: A Borderline Ligand Field Case. Crystals (MDPI), 2020,10,477, DOI: 10.3390/cryst10060477
Riccardo Destro*, Riccardo Ruffo, Pietro Roversi, Raffaella Soave, Laura Loconte, Leonardo Lo Presti: Anharmonic motions versus dynamic disorder at the Mg ion from the charge densities in pyrope (Mg3Al2Si3O12) crystals at 30 K: Six of one, half a dozen of the other. Acta Crystallographica Section B: Structural Science, 04/2017; 73, 722–736, DOI: 10.1107/S2052520617006102
Giovanni Macetti, Laura Loconte, Silvia Rizzato, Carlo Gatti, Leonardo Lo Presti*: Intermolecular Recognition of the Antimalarial Drug Chloroquine: A Quantum Theory of Atoms in Molecules–Density Functional Theory Investigation of the Hydrated Dihydrogen Phosphate Salt from the 103 K X-ray Structure. Crystal Growth & Design 09/2016; 16(10):6043–6054., DOI:10.1021/acs.cgd.6b01069
Carlo Gatti*, Ahmed Muhammed Orlando, Leonardo Lo Presti: Insights on Spin Polarization through the Spin Density Source Function. Chemical Science 04/2015; 6(7):3845-3852., DOI:10.1039/C4SC03988B
Leonardo Lo Presti*, Mattia Sist, Laura Loconte, Andrea Pinto, Lucia Tamborini, Carlo Gatti: Rationalizing the Lacking of Inversion Symmetry in a Noncentrosymmetric Polar Racemate: An Experimental and Theoretical Study. Crystal Growth & Design 10/2014; 14(11):5822–5833., DOI:10.1021/cg501074x
Leonardo Lo Presti,* Ahmed M. Orlando, Laura Loconte, Riccardo Destro, Emanuele Ortoleva, Raffaella Soave, Carlo Gatti*: Single N–C Bond Becomes Shorter than a Formally Double N═C Bond in a Thiazete-1,1-dioxide Crystal: An Experimental and Theoretical Study of Strong Crystal Field Effects. Crystal Growth & Design 08/2014; 14:4418-4429., DOI:10.1021/cg500518a
Riccardo Destro*, Elisabetta Sartirana, Laura Loconte, Raffaella Soave, Pietro Colombo, Claudio Destro, Leonardo Lo Presti: Competing C═O···C═O, C–H···O, Cl···O, and Cl···Cl Interactions Governing the Structural Phase Transition of 2,6-Dichloro-p-benzoquinone at Tc = 122.6 K. Crystal Growth & Design 08/2013; 13(10-10):4571-4582. DOI: 10.1021/cg401123s
Gabriele Saleh, Raffaella Soave*, Leonardo Lo Presti*, Riccardo Destro: Progress in the Understanding of the Key Pharmacophoric Features of the Antimalarial Drug Dihydroartemisinin: An Experimental and Theoretical Charge Density Study. Chemistry - A European Journal 01/2013; 19(10):3490–3503., DOI:10.1002/chem.201202486
Gabriele Saleh, Carlo Gatti*, Leonardo Lo Presti*, Julia Contreras-García: Revealing Non-Covalent Interactions in Molecular Crystals through Their Experimental Electron Densities.. Chemistry - A European Journal 10/2012; 18(48):15523–15536., DOI:10.1002/chem.201201290
Leonardo Lo Presti*, Arkady Ellern, Riccardo Destro*, Raffaella Soave, Bruno Lunelli: Rationalizing the Effect of Halogenation on the Molecular Structure of Simple Cyclobutene Derivatives by Topological Real-Space Analysis of Their Electron Density. The Journal of Physical Chemistry A 07/2011; 115(45):12695-707. DOI: 10.1021/jp203615x
Leonardo Lo Presti*, Carlo Gatti*: Using the Source Function descriptor to dampen the multipole model bias in charge density studies from X-ray structure factors refinements. Chemical Physics Letters 2009, 476, 308-316 DOI: 0.1016/j.cplett.2009.06.022
Leonardo Lo Presti*, Arkady Ellern, Riccardo Destro, Bruno Lunelli: Effect of Methoxy Substituents on the Structural and Electronic Properties of Fluorinated Cyclobutenes: A Study of Hexafluorocyclobutene and Its Vinyl Methoxy Derivatives by XRD and Periodic DFT Calculations. The Journal of Physical Chemistry A 05/2009; 113(13):3186-96., DOI:10.1021/jp8084809
Leonardo Lo Presti*, Riccardo Destro: Experimental and theoretical charge density distribution of the colossal magnetoresistive transition metal sulfide FeCr2S4. The Journal of Chemical Physics 02/2008; 128(4):044710., DOI:10.1063/1.2822160
Leonardo Lo Presti*, Raffaella Soave, Riccardo Destro: On the Interplay between CH···O and OH···O Interactions in Determining Crystal Packing and Molecular Conformation: An Experimental and Theoretical Charge Density Study of the Fungal Secondary Metabolite Austdiol (C12H12O5). The Journal of Physical Chemistry B 04/2006; 110(12):6405-14., DOI:10.1021/jp056823y
Riccardo Destro*, Raffaella Soave, Mario Barzaghi, Leonardo Lo Presti: Progress in the Understanding of Drug-Receptor Interactions, Part 1: Experimental Charge-Density Study of an Angiotensin II Receptor Antagonist (C30H30N6O3S) at T=17 K. Chemistry–A european Journal 08/2005; 11(16):4621-34., DOI:10.1002/chem.200400964
Riccardo Destro*, Laura Loconte, Leonardo Lo Presti, Pietro Roversi, Raffaella Soave: On the role of data quality in experimental charge-density studies. Acta Crystallographica Section A Foundations of Crystallography 10/2004; 60(Pt 5):365-70., DOI:10.1107/S0108767304014813
