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
Multipolar refinements of structural models fitting extensive sets of X-ray diffraction (XRD) data from single crystals of 1,3-bis(dimethylamino)squaraine [SQ, C<sub>8</sub>H<sub>12</sub>N<sub>2</sub>O<sub>2</sub>] and its dihydrate [SQDH, C<sub>...
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MDPI AG
2020-10-01
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| Series: | Crystals |
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| Online Access: | https://www.mdpi.com/2073-4352/10/10/894 |
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| author | Riccardo Destro Pietro Roversi Raffaella Soave Arjan Hovestad Leonardo Lo Presti |
| author_facet | Riccardo Destro Pietro Roversi Raffaella Soave Arjan Hovestad Leonardo Lo Presti |
| author_sort | Riccardo Destro |
| collection | DOAJ |
| description | Multipolar refinements of structural models fitting extensive sets of X-ray diffraction (XRD) data from single crystals of 1,3-bis(dimethylamino)squaraine [SQ, C<sub>8</sub>H<sub>12</sub>N<sub>2</sub>O<sub>2</sub>] and its dihydrate [SQDH, C<sub>8</sub>H<sub>12</sub>N<sub>2</sub>O<sub>2</sub>·2H<sub>2</sub>O], collected at very low T (18 ± 1 K for SQ, 20 ± 1 K for SQDH), led to an accurate description of their crystal electron density distributions. Atomic volumes and charges have been estimated from the experimental charge densities using the Quantum Theory of Atoms in Molecules (QTAIM) formalism. Our analysis confirms the common representation (in the literature and textbooks) of the squaraine central, four-membered squarylium ring as carrying two positive charges, a representation that has been recently questioned by some theoretical calculations: the integrated total charge on the C4 fragment is estimated as ca. +2.4e in SQ and +2.2e in SQDH. The topology of the experimental electron density for the SQ squaraine molecule is modified in the dihydrated crystal by interactions between the methyl groups and the H<sub>2</sub>O molecules in the crystal. Maps of the molecular electrostatic potential in the main molecular planes in both crystals clearly reveal the quadrupolar charge distribution of the squaraine molecules. Molecular quadrupole tensors, as calculated with the PAMoC package using both Stewart and QTAIM distributed multipole analysis (DMA), are the same within experimental error. |
| first_indexed | 2024-03-10T15:52:43Z |
| format | Article |
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| issn | 2073-4352 |
| language | English |
| last_indexed | 2024-03-10T15:52:43Z |
| publishDate | 2020-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Crystals |
| spelling | doaj.art-4cf2194963d84b68a6aa3b6479e6710d2023-11-20T15:55:39ZengMDPI AGCrystals2073-43522020-10-01101089410.3390/cryst10100894Experimental 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 DataRiccardo Destro0Pietro Roversi1Raffaella Soave2Arjan Hovestad3Leonardo Lo Presti4Department of Chemistry, Università degli Studi di Milano, Via Golgi 19, 20133 Milano, ItalyLeicester Institute of Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Lancaster Road, Leicester LE1 7HB, UKIstituto di Scienze e Tecnologie Chimiche “Giulio Natta” (SCITEC), Italian Research Council, Via Golgi 19, 20133 Milano, ItalyMECO Equipment Engineers B.V., Marconilaan 2, 5151 DR Drunen, The NetherlandsDepartment of Chemistry, Università degli Studi di Milano, Via Golgi 19, 20133 Milano, ItalyMultipolar refinements of structural models fitting extensive sets of X-ray diffraction (XRD) data from single crystals of 1,3-bis(dimethylamino)squaraine [SQ, C<sub>8</sub>H<sub>12</sub>N<sub>2</sub>O<sub>2</sub>] and its dihydrate [SQDH, C<sub>8</sub>H<sub>12</sub>N<sub>2</sub>O<sub>2</sub>·2H<sub>2</sub>O], collected at very low T (18 ± 1 K for SQ, 20 ± 1 K for SQDH), led to an accurate description of their crystal electron density distributions. Atomic volumes and charges have been estimated from the experimental charge densities using the Quantum Theory of Atoms in Molecules (QTAIM) formalism. Our analysis confirms the common representation (in the literature and textbooks) of the squaraine central, four-membered squarylium ring as carrying two positive charges, a representation that has been recently questioned by some theoretical calculations: the integrated total charge on the C4 fragment is estimated as ca. +2.4e in SQ and +2.2e in SQDH. The topology of the experimental electron density for the SQ squaraine molecule is modified in the dihydrated crystal by interactions between the methyl groups and the H<sub>2</sub>O molecules in the crystal. Maps of the molecular electrostatic potential in the main molecular planes in both crystals clearly reveal the quadrupolar charge distribution of the squaraine molecules. Molecular quadrupole tensors, as calculated with the PAMoC package using both Stewart and QTAIM distributed multipole analysis (DMA), are the same within experimental error.https://www.mdpi.com/2073-4352/10/10/894single crystalX-ray diffractioncharge densitysquarainelow temperatureQuantum Theory of Atoms in Molecules |
| spellingShingle | 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 single crystal X-ray diffraction charge density squaraine low temperature Quantum Theory of Atoms in Molecules |
| title | 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 |
| title_full | 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 |
| title_fullStr | 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 |
| title_full_unstemmed | 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 |
| title_short | 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 |
| title_sort | 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 |
| topic | single crystal X-ray diffraction charge density squaraine low temperature Quantum Theory of Atoms in Molecules |
| url | https://www.mdpi.com/2073-4352/10/10/894 |
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