Molekular neben ionisch: Kristallstrukturen eines 1/1- und eines 1/4-Addukts aus Pyridin und Ameisensäure

Mechanical mixing of solid dicarboxylic acids of variable chain length HOOC(CH(2))(n)COOH (n = 1-7) with solid 1,4-diazabicyclo[2.2.2]octane generates the corresponding salts or co-crystals of the formula [N(CH(2)CH(2))(3)N]-H-[OOC(CH(2))(n)COOH] (n=1-7). Preparation of the same systems from solution has been instrumental for a full characterization of the mechanochemical products by means of single-crystal and powder-diffraction X-ray analyses, as well as by solid-state NMR. The acid-base adducts, whether involving proton transfer from the COOH group to the N-acceptor, that is having ((-))O...H-N((+)) interactions, or the formation of neutral O-H...N hydrogen bonds, show a melting point alternation phenomenon analogous to that shown by the neutral carboxylic acids. The carbon chemical shift tensors of the COOH group obtained from the sideband intensity of low speed spinning NMR spectra provide a reliable criterion for assigning the protonation state of the adducts.

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Mechanochemical Preparation of Hydrogen‐Bonded Adducts Between the Diamine 1,4‐Diazabicyclo[2.2.2]octane and Dicarboxylic Acids of Variable Chain Length: An X‐ray Diffraction and Solid‐State NMR Study

Braga

Maini

Sanctis

et al. 2003

Chemistry A European J

107

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Assembly of Hybrid Organic–Organometallic Materials through Mechanochemical Acid–Base Reactions

Braga

Maini

Polito

et al. 2003

Chemistry A European J

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Manual grinding of the organometallic complex [Fe(eta(5)-C(5)H(4)COOH)(2)] with a number of solid bases, namely 1,4-diazabicyclo[2.2.2]octane, C(6)H(12)N(2), 1,4-phenylenediamine, p-(NH(2))(2)C(6)H(4), piperazine, HN(C(2)H(4))(2)NH, trans-1,4-cyclohexanediamine, p-(NH(2))(2)C(6)H(10), and guanidinium carbonate [(NH(2))(3)C](2)[CO(3)], generates quantitatively the corresponding adducts, [HC(6)H(12)N(2)][Fe(eta(5)-C(5)H(4)COOH)(eta(5)-C(5)H(4)COO)] (1), [HC(6)H(8)N(2)][Fe(eta(5)-C(5)H(4)COOH)(eta(5)-C(5)H(4)COO)] (2), [H(2)C(4)H(10)N(2)][Fe(eta(5)-C(5)H(4)COO)(2)] (3), [H(2)C(6)H(14)N(2)][Fe(eta(5)-C(5)H(4)COO)(2)].2 H(2)O, (4.2 H(2)O), and [C(NH(2))(3)](2)[Fe(eta(5)-C(5)H(4)COO)(2)].2 H(2)O, (5.2 H(2)O), respectively. Crystallization from methanol in the presence of seeds of the ground sample allows the growth of single crystals of these adducts; therefore we were able to determine the structures of the adducts by single-crystal X-ray diffraction. This information was used in turn to identify and characterize the polycrystalline materials obtained by the grinding process. In the case of [HC(6)N(2)H(12)][Fe(eta(5)-C(5)H(4)COOH)(eta(5)-C(5)H(4)COO)] (1), the base can be removed by mild treatment regenerating the starting dicarboxylic acid, while in all other cases decomposition is observed. The solid-solid processes described herein imply molecular diffusion through the lattice, breaking and reassembling of hydrogen-bonded networks, and proton transfer from acid to base.

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Three Polymorphic Forms of the Co‐Crystal 4,4′‐Bipyridine/Pimelic Acid and their Structural, Thermal, and Spectroscopic Characterization

Braga

Palladino

Polito

et al. 2008

Chemistry A European J

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Three crystal forms of the co-crystal 4,4'-bipy/pimelic acid (bipy: bipyridine), [NH(4)C(5)-C(5)H(4)N][HOOC(CH(2))(5)COOH], have been prepared and their relationship investigated by single-crystal X-ray diffraction, variable-temperature X-ray powder diffraction, differential scanning calorimetry and solid-state NMR spectroscopy. Both X-ray and NMR spectroscopic results indicate that no proton transfer takes place, that is, the three crystal forms are true co-crystals of neutral molecules. Forms I and II both convert into Form III at high temperature, Forms II and III being the thermodynamically stable forms at room and high temperature, respectively.

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Molekular neben ionisch: Kristallstrukturen eines 1/1- und eines 1/4-Addukts aus Pyridin und Ameisensäure

Cited by 3 publications

References 10 publications

Mechanochemical Preparation of Hydrogen‐Bonded Adducts Between the Diamine 1,4‐Diazabicyclo[2.2.2]octane and Dicarboxylic Acids of Variable Chain Length: An X‐ray Diffraction and Solid‐State NMR Study

Mechanochemical Preparation of Hydrogen‐Bonded Adducts Between the Diamine 1,4‐Diazabicyclo[2.2.2]octane and Dicarboxylic Acids of Variable Chain Length: An X‐ray Diffraction and Solid‐State NMR Study

Assembly of Hybrid Organic–Organometallic Materials through Mechanochemical Acid–Base Reactions

Three Polymorphic Forms of the Co‐Crystal 4,4′‐Bipyridine/Pimelic Acid and their Structural, Thermal, and Spectroscopic Characterization

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