Tautomeric Equilibrium of an Asymmetric β-Diketone in Halogen-Bonded Cocrystals with Perfluorinated Iodobenzenes

Martinez, Valentina; Bedeković, Nikola; Stilinović, Vladimir; Cinčić, Dominik

doi:10.3390/cryst11060699

Cited by 7 publications

(5 citation statements)

References 63 publications

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“…To date, various Lewis bases (neutral molecules or charged species) have been employed as halogen bond acceptors in constructing halogenbonded supramolecular assemblies. These have most commonly been organic [13,14] and metal-organic [15] molecules containing electron-rich nitrogen [16][17][18][19][20][21][22][23][24][25][26] and oxygen atoms [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41], as well as inorganic anions such as halogenides [42][43][44][45][46][47][48][49][50][51][52][53][54]. The most commonly used halogen bond donors have traditionally been neutral organic molecules where a halogen atom is bonded to electron-withdrawing molecular residues.…”

Section: Introductionmentioning

confidence: 99%

Halogen Bonding in N-Alkyl-3-halogenopyridinium Salts

Fotović

Stilinović

2021

Crystals

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We performed a structural study of N-alkylated halogenopyridinium cations to examine whether choice of the N-substituent has any considerable effect on the halogen bonding capability of the cations. For that purpose, we prepared a series of N-ethyl-3-halopyridinium iodides and compared them with their N-methyl-3-halopyridinium analogues. Structural analysis revealed that N-ethylated halogenopyridinium cations form slightly shorter C−X⋯I− halogen bonds with iodide anion. We have also attempted synthesis of ditopic symmetric bis-(3-iodopyridinium) dications. Although successful in only one case, the syntheses have afforded two novel ditopic asymmetric monocations with an iodine atom bonded to the pyridine ring and another on the aliphatic N-substituent. Here, the C−I⋯I− halogen bond lengths involving pyridine iodine atom were notably shorter than those involving an aliphatic iodine atom as a halogen bond donor. This trend in halogen bond lengths is in line with the charge distribution on the Hirshfeld surfaces of the cations—the positive charge is predominantly located in the pyridine ring making the pyridine iodine atom σ-hole more positive than the one on the alkyl chan.

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Section: Introductionmentioning

confidence: 99%

Halogen Bonding in N-Alkyl-3-halogenopyridinium Salts

Fotović

Stilinović

2021

Crystals

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“…This is due to the weaker basicity of oxygen compared to the iminic nitrogen of the pyrazole moiety. For similar motifs, such as pyridyl substituted β-diketones, I⋯O keto amounts to about 3.05 Å (refcodes TAXYID [ 45 ], AWUWOH ‡ [ 46 ]). In all cases of protonated β-diketones, the halogen bond acceptor is the keto oxygen, not the enol bond acceptor.…”

Section: Resultsmentioning

confidence: 99%

Three for the Price of One: Concomitant I⋯N, I⋯O, and I⋯π Halogen Bonds in the Same Crystal Structure

2022

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The ditopic molecule 3-(1,3,5-trimethyl-1H-4-pyrazolyl)pentane-2,4-dione (HacacMePz) combines two different Lewis basic sites. It forms a crystalline adduct with the popular halogen bond (XB) donor 2,3,5,6-tetrafluoro-1,4-diiodobenzene (TFDIB) with a HacacMePz:TFDIB ratio of 2 : 3. In a simplified picture, the topology of the adduct corresponds to a hcb net. In addition to the expected acetylacetone keto O and pyrazole N acceptor sites, a third and less common short contact to a TFDIB iodine is observed: The acceptor site is again the most electron-rich site of the pyrazole π-system. This iminic N atom is thus engaged as the acceptor in two orthogonal halogen bonds. Evaluation of the geometric results and of a single-point calculation agree with respect to the strength of the intermolecular contacts: The conventional N···I XB is the shortest (2.909(4) Å) and associated with the highest electron density (0.150 eÅ−3) in the bond critical point (BCP), followed by the O···I contact (2.929(3) Å, 0.109 eÅ−3), and the π contact (3.2157(3) Å, 0.075 eÅ−3). If one accepts the idea of deducing interaction energies from energy densities at the BCP, the short contacts also follow this sequence. Two more criteria identify the short N···I contact as the most relevant: The associated C–I bond is significantly longer than the database average, and it is the only intermolecular interaction with a negative total energy density in the BCP.

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“…The carbonyl oxygen has also been demonstrated to be a viable halogen bond (XB) acceptor, albeit weaker and less reliable than sp 2 nitrogen. − The question therefore arises whether a combination of pyridone and appropriate halogen bond donors would lead to structures in which the pyridone homosynthon is retained (Scheme d) or the introduction of a halogen bond donor would disrupt the pyridone homosynthon, possibly even stabilizing the hydroxypyridine tautomer via an X···N(sp 2 ) halogen bond.…”

Section: Introductionmentioning

confidence: 99%

Conservation of the Hydrogen-Bonded Pyridone Homosynthon in Halogen-Bonded Cocrystals

Bedeković

Fotović

Stilinović

et al. 2022

Crystal Growth & Design

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Seven cocrystals of pyridone and perfluorinated halocarbons have been prepared. In all cases pairs of pyridone molecules are connected into dimers by two N–H···O hydrogen bonds, forming the characteristic pyridone homosynthon of R 2 2 (8) topology. These dimers further act as acceptors of halogen bonds through the two pyridone oxygen atoms, forming two (in six cases) or three (in one case) halogen bonds with the donor molecules. The stoichiometry of the cocrystals obtained and the overall topology of the supramolecular architecture depend primarily on the topicity of the halogen bond donor, with the monotopic donor yielding a cocrystal of 1:1 stoichiometry comprising discrete supramolecular complexes, the ditopic donors cocrystals of 1:2 stoichiometry comprising chains, and the tritopic donor a cocrystal of 1:2 stoichiometry comprising hydrogen- and halogen-bonded layers. The results indicate that the pyridone homosynthon is a robust and reliable supramolecular synthon that is conserved in halogen-bonded cocrystals of pyridone.

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Tautomeric Equilibrium of an Asymmetric β-Diketone in Halogen-Bonded Cocrystals with Perfluorinated Iodobenzenes

Cited by 7 publications

References 63 publications

Halogen Bonding in N-Alkyl-3-halogenopyridinium Salts

Halogen Bonding in N-Alkyl-3-halogenopyridinium Salts

Three for the Price of One: Concomitant I⋯N, I⋯O, and I⋯π Halogen Bonds in the Same Crystal Structure

Conservation of the Hydrogen-Bonded Pyridone Homosynthon in Halogen-Bonded Cocrystals

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