13 research outputs found

    Accurate Modeling of Organic Molecular Crystals by Dispersion-Corrected Density Functional Tight Binding (DFTB)

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    The ambitious goal of organic crystal structure prediction challenges theoretical methods regarding their accuracy and efficiency. Dispersion-corrected density functional theory (DFT-D) in principle is applicable, but the computational demands, for example, to compute a huge number of polymorphs, are too high. Here, we demonstrate that this task can be carried out by a dispersion-corrected density functional tight binding (DFTB) method. The semiempirical Hamiltonian with the D3 correction can accurately and efficiently model both solid- and gas-phase inter- and intramolecular interactions at a speed up of 2 orders of magnitude compared to DFT-D. The mean absolute deviations for interaction (lattice) energies for various databases are typically 2–3 kcal/mol (10–20%), that is, only about two times larger than those for DFT-D. For zero-point phonon energies, small deviations of <0.5 kcal/mol compared to DFT-D are obtained

    Theoretical considerations from On the hydrogen activation by frustrated Lewis pairs in the solid state: benchmark studies and theoretical insights

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    Recently, the concept of small molecule activation by frustrated Lewis pairs (FLPs) has been expanded to the solid state showing a variety of interesting reactivities. Therefore, there is a need to establish a computational protocol to investigate such systems theoretically. In the present study, we selected several FLPs and applied multiple levels of theory, ranging from a semi-empirical tight-binding Hamiltonian to dispersion corrected hybrid density functionals. Their performance is benchmarked for the computation of crystal geometries, thermostatistical contributions, and reaction energies. We show that the computationally efficient HF-3c method gives accurate crystal structures and is numerically stable and sufficiently fast for routine applications. This method also gives reliable values for the thermostatistical contributions to Gibbs free energies. The meta-GGA TPSS-D3 evaluated in a projector augmented plane wave basis set is able to produce reaction electronic energies. The established protocol is intended to support experimental studies and to predict new reactions in the emerging field of solid-state FLPs

    Low-Cost Quantum Chemical Methods for Noncovalent Interactions

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    The efficient and reasonably accurate description of noncovalent interactions is important for various areas of chemistry, ranging from supramolecular host–guest complexes and biomolecular applications to the challenging task of crystal structure prediction. While London dispersion inclusive density functional theory (DFT-D) can be applied, faster “low-cost” methods are required for large-scale applications. In this Perspective, we present the state-of-the-art of minimal basis set, semiempirical molecular-orbital-based methods. Various levels of approximations are discussed based either on canonical Hartree–Fock or on semilocal density functionals. The performance for intermolecular interactions is examined on various small to large molecular complexes and organic solids covering many different chemical groups and interaction types. We put the accuracy of low-cost methods into perspective by comparing with first-principle density functional theory results. The mean unsigned deviations of binding energies from reference data are typically 10–30%, which is only two times larger than those of DFT-D. In particular, for neutral or moderately polar systems, many of the tested methods perform very well, while at the same time, computational savings of up to 2 orders of magnitude can be achieved

    Geometrical Correction for the Inter- and Intramolecular Basis Set Superposition Error in Periodic Density Functional Theory Calculations

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    We extend the previously developed geometrical correction for the inter- and intramolecular basis set superposition error (gCP) to periodic density functional theory (DFT) calculations. We report gCP results compared to those from the standard Boys–Bernardi counterpoise correction scheme and large basis set calculations. The applicability of the method to molecular crystals as the main target is tested for the benchmark set X23. It consists of 23 noncovalently bound crystals as introduced by Johnson et al. (J. Chem. Phys. 2012, 137, 054103) and refined by Tkatchenko et al. (J. Chem. Phys. 2013, 139, 024705). In order to accurately describe long-range electron correlation effects, we use the standard atom-pairwise dispersion correction scheme DFT-D3. We show that a combination of DFT energies with small atom-centered basis sets, the D3 dispersion correction, and the gCP correction can accurately describe van der Waals and hydrogen-bonded crystals. Mean absolute deviations of the X23 sublimation energies can be reduced by more than 70% and 80% for the standard functionals PBE and B3LYP, respectively, to small residual mean absolute deviations of about 2 kcal/mol (corresponding to 13% of the average sublimation energy). As a further test, we compute the interlayer interaction of graphite for varying distances and obtain a good equilibrium distance and interaction energy of 6.75 Å and −43.0 meV/atom at the PBE-D3-gCP/SVP level. We fit the gCP scheme for a recently developed pob-TZVP solid-state basis set and obtain reasonable results for the X23 benchmark set and the potential energy curve for water adsorption on a nickel (110) surface

    An Enamine/HB(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> Adduct as a Dormant State in Frustrated Lewis Pair Chemistry

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    The enamine piperidinocyclopentene reacts with HB­(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> by formation of the C-Lewis base/B-Lewis acid adduct <b>10</b>. It shows a zwitterionic iminium ion/hydridoborate structure. However, this adduct formation is apparently reversible and may generate the “invisible” frustrated Lewis pair <b>11</b> as a reactive intermediate by hydroboration of the enamine CC bond in an equilibrium situation at room temperature. Consequently, the FLP <b>11</b> was trapped by typical FLP reactions, namely by the reaction with dihydrogen to give the ammonium/hydridoborate <b>12</b>, the acetylene deprotonation products <b>13</b> and <b>14</b>, and simple borane adducts with pyridine (<b>15</b>) and with an isonitrile (<b>17</b>). The products <b>10</b> and <b>12</b>–<b>15</b> and the isonitrile adduct <b>17</b> were characterized by X-ray diffraction. A DFT study determined the thermodynamic features of the <b>10</b> ⇄ <b>11</b> equilibrium and of a previously discussed reference system (<b>18</b> ⇄ <b>19</b>) derived by reacting piperidinocyclohexene with HB­(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>

    An Enamine/HB(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> Adduct as a Dormant State in Frustrated Lewis Pair Chemistry

    No full text
    The enamine piperidinocyclopentene reacts with HB­(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> by formation of the C-Lewis base/B-Lewis acid adduct <b>10</b>. It shows a zwitterionic iminium ion/hydridoborate structure. However, this adduct formation is apparently reversible and may generate the “invisible” frustrated Lewis pair <b>11</b> as a reactive intermediate by hydroboration of the enamine CC bond in an equilibrium situation at room temperature. Consequently, the FLP <b>11</b> was trapped by typical FLP reactions, namely by the reaction with dihydrogen to give the ammonium/hydridoborate <b>12</b>, the acetylene deprotonation products <b>13</b> and <b>14</b>, and simple borane adducts with pyridine (<b>15</b>) and with an isonitrile (<b>17</b>). The products <b>10</b> and <b>12</b>–<b>15</b> and the isonitrile adduct <b>17</b> were characterized by X-ray diffraction. A DFT study determined the thermodynamic features of the <b>10</b> ⇄ <b>11</b> equilibrium and of a previously discussed reference system (<b>18</b> ⇄ <b>19</b>) derived by reacting piperidinocyclohexene with HB­(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>

    An Enamine/HB(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> Adduct as a Dormant State in Frustrated Lewis Pair Chemistry

    No full text
    The enamine piperidinocyclopentene reacts with HB­(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> by formation of the C-Lewis base/B-Lewis acid adduct <b>10</b>. It shows a zwitterionic iminium ion/hydridoborate structure. However, this adduct formation is apparently reversible and may generate the “invisible” frustrated Lewis pair <b>11</b> as a reactive intermediate by hydroboration of the enamine CC bond in an equilibrium situation at room temperature. Consequently, the FLP <b>11</b> was trapped by typical FLP reactions, namely by the reaction with dihydrogen to give the ammonium/hydridoborate <b>12</b>, the acetylene deprotonation products <b>13</b> and <b>14</b>, and simple borane adducts with pyridine (<b>15</b>) and with an isonitrile (<b>17</b>). The products <b>10</b> and <b>12</b>–<b>15</b> and the isonitrile adduct <b>17</b> were characterized by X-ray diffraction. A DFT study determined the thermodynamic features of the <b>10</b> ⇄ <b>11</b> equilibrium and of a previously discussed reference system (<b>18</b> ⇄ <b>19</b>) derived by reacting piperidinocyclohexene with HB­(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>

    An Enamine/HB(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> Adduct as a Dormant State in Frustrated Lewis Pair Chemistry

    No full text
    The enamine piperidinocyclopentene reacts with HB­(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> by formation of the C-Lewis base/B-Lewis acid adduct <b>10</b>. It shows a zwitterionic iminium ion/hydridoborate structure. However, this adduct formation is apparently reversible and may generate the “invisible” frustrated Lewis pair <b>11</b> as a reactive intermediate by hydroboration of the enamine CC bond in an equilibrium situation at room temperature. Consequently, the FLP <b>11</b> was trapped by typical FLP reactions, namely by the reaction with dihydrogen to give the ammonium/hydridoborate <b>12</b>, the acetylene deprotonation products <b>13</b> and <b>14</b>, and simple borane adducts with pyridine (<b>15</b>) and with an isonitrile (<b>17</b>). The products <b>10</b> and <b>12</b>–<b>15</b> and the isonitrile adduct <b>17</b> were characterized by X-ray diffraction. A DFT study determined the thermodynamic features of the <b>10</b> ⇄ <b>11</b> equilibrium and of a previously discussed reference system (<b>18</b> ⇄ <b>19</b>) derived by reacting piperidinocyclohexene with HB­(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>

    An Enamine/HB(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> Adduct as a Dormant State in Frustrated Lewis Pair Chemistry

    No full text
    The enamine piperidinocyclopentene reacts with HB­(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> by formation of the C-Lewis base/B-Lewis acid adduct <b>10</b>. It shows a zwitterionic iminium ion/hydridoborate structure. However, this adduct formation is apparently reversible and may generate the “invisible” frustrated Lewis pair <b>11</b> as a reactive intermediate by hydroboration of the enamine CC bond in an equilibrium situation at room temperature. Consequently, the FLP <b>11</b> was trapped by typical FLP reactions, namely by the reaction with dihydrogen to give the ammonium/hydridoborate <b>12</b>, the acetylene deprotonation products <b>13</b> and <b>14</b>, and simple borane adducts with pyridine (<b>15</b>) and with an isonitrile (<b>17</b>). The products <b>10</b> and <b>12</b>–<b>15</b> and the isonitrile adduct <b>17</b> were characterized by X-ray diffraction. A DFT study determined the thermodynamic features of the <b>10</b> ⇄ <b>11</b> equilibrium and of a previously discussed reference system (<b>18</b> ⇄ <b>19</b>) derived by reacting piperidinocyclohexene with HB­(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>

    An Enamine/HB(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> Adduct as a Dormant State in Frustrated Lewis Pair Chemistry

    No full text
    The enamine piperidinocyclopentene reacts with HB­(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> by formation of the C-Lewis base/B-Lewis acid adduct <b>10</b>. It shows a zwitterionic iminium ion/hydridoborate structure. However, this adduct formation is apparently reversible and may generate the “invisible” frustrated Lewis pair <b>11</b> as a reactive intermediate by hydroboration of the enamine CC bond in an equilibrium situation at room temperature. Consequently, the FLP <b>11</b> was trapped by typical FLP reactions, namely by the reaction with dihydrogen to give the ammonium/hydridoborate <b>12</b>, the acetylene deprotonation products <b>13</b> and <b>14</b>, and simple borane adducts with pyridine (<b>15</b>) and with an isonitrile (<b>17</b>). The products <b>10</b> and <b>12</b>–<b>15</b> and the isonitrile adduct <b>17</b> were characterized by X-ray diffraction. A DFT study determined the thermodynamic features of the <b>10</b> ⇄ <b>11</b> equilibrium and of a previously discussed reference system (<b>18</b> ⇄ <b>19</b>) derived by reacting piperidinocyclohexene with HB­(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>
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