"Organic Fluorine" and its Importance in Crystal Engineering

The phrase "Organic fluorine" [1] was introduced by Dunitz and Taylor in 1997 to identify the C–F bonds in organic systems. Different research groups have used the phrase to glorify or deny the influence of C–F bond in crystal lattices. Once Dunitz stated that "Organic Fluorine: Odd Man Out" and Howard et al. questioned the role of "Organic fluorine" in crystal engineering. While some researchers have refuted the role of "organic fluorine" in crystal packing; the others indicated the importance of the interactions involving the same group. A number of publications have shown the importance of "Organic fluorine" in influencing crystal packing. We have been interested in the area of weak interactions in organic solid state chemistry since 1999 [2]; especially interactions involving "Organic fluorine". The study is being conducted following a systematic approach and is still in progress. We have looked at the structures of a number if tetrahydroisoquinoline derivatives, a number of differently substituted imines, phenyleacetanilydes, benzanilides and azobenzenes [3] etc. in order to elucidate the influence of "Organic fluorine" in crystal engineering both in the presence and in the absence of strong hydrogen bonding functional groups present within the molecule. A short summary of our observations will be highlighted in the presentation.

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Synthon robustness by C-F groups in halogen substituted N-benzylideneanilines

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314081893 ◽

2014 ◽

Vol 70 (a1) ◽

pp. C1811-C1811

Author(s):

Gurpreet Kaur ◽

Angshuman Roy Choudhury

Keyword(s):

Crystal Structure ◽

Crystal Engineering ◽

Crystal Packing ◽

Weak Interactions ◽

Topological Analysis ◽

Strong Hydrogen Bond ◽

Hydrogen Bond Donor ◽

Donor And Acceptor ◽

The Impact ◽

Organic Fluorine

The arrangement of the molecules in their crystal structure is controlled by the non-covalent intermolecular interactions other than the effectual space filling. The role of strong hydrogen bonds in guiding the crystal packing is well-known in the literature. But, how significant are the weak interactions in the field of crystal engineering, has yet not been fully understood. Our aim is to comprehend the nature and strength of the weak interactions involving fluorine in guiding the packing of small organic molecules in their respective crystal structure. The reason being the controversies, which are involved regarding the interactions offered by "organic fluorine"[1] and also due to the importance of these interactions in the pharmaceutical industry. Some of the research groups indicate the incapability of interactions offered by fluorine in the formation of supramolecular motifs, whereas other groups have indicated that substantial role is being played by fluorine in constructing the lattice through C-H···F, C-F···F and C-F···π interactions in the presence and absence of strong hydrogen bond donor and acceptor groups. To understand more about these interactions, we have chosen a model system of halogen substituted N-benzylideneanilines[2]. In this system, we have analysed the impact of fluorine mediated interactions on the crystal packing by having fluorine as a substituent on both the phenyl rings. Then the robustness of the synthons offered by organic fluorine has been anticipated in the same system, but with one of the substituent as chlorine or bromine in either of the phenyl ring. It has been observed that the replacement of the non-interacting fluorine by its heavier analogue has not altered the supramolecular motif, which was formed by the other fluorine. But the crystal packing has been found to be completely altered in the molecules where the interacting fluorine was replaced by its heavier analogue. Salient features of our computational studies, which include the calculation of the stabilization energies of the studied dimers using MP2 method and their topological analysis using AIM2000, to support the experimental observations will also be presented to highlight the sturdiness of the synthons formed by so called "organic fluorine".

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Synthesis of a New Series of Organic Solid-State Near-Infrared Emitters: The Role of Crystal Packing and Weak Intermolecular Interactions and Application in Latent Fingerprint Detection

Crystal Growth & Design ◽

10.1021/acs.cgd.0c01392 ◽

2021 ◽

Vol 21 (2) ◽

pp. 1062-1076

Author(s):

Ranjit Singh ◽

Abhishek Kumar Gupta ◽

Chullikkattil P. Pradeep

Keyword(s):

Solid State ◽

Intermolecular Interactions ◽

Near Infrared ◽

Crystal Packing ◽

Latent Fingerprint ◽

Weak Intermolecular Interactions ◽

Organic Solid ◽

Infrared Emitters ◽

Fingerprint Detection

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The role of weak interactions in the crystal packing of two novel 1D Hg(II) coordination polymers and investigation for preparation of their rod and spherical structures

Inorganica Chimica Acta ◽

10.1016/j.ica.2019.119243 ◽

2020 ◽

Vol 501 ◽

pp. 119243 ◽

Cited By ~ 1

Author(s):

Ghodrat Mahmoudi ◽

Payam Hayati ◽

Khosro Mohammadi ◽

Ardavan Masoudiasl ◽

Joel T. Mague ◽

...

Keyword(s):

Coordination Polymers ◽

Crystal Packing ◽

Weak Interactions ◽

Spherical Structures

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Tuning colour in multi-component complexes: Molecular disorder as a design tool

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s205327331408992x ◽

2014 ◽

Vol 70 (a1) ◽

pp. C1007-C1007

Author(s):

Charlotte Jones ◽

Chick Wilson ◽

Lynne Thomas

Keyword(s):

Single Crystal ◽

Crystal Engineering ◽

Crystal Packing ◽

Colour Change ◽

Molecular Complexes ◽

Design Tool ◽

Layered Crystal ◽

Molecular Rearrangement ◽

Organic Systems ◽

Inorganic Systems

The key aim of multi-component crystallisation is modification of the physicochemical properties for a specific task.[1] Tuning colour using molecular components is a relatively unexplored area, which is surprising given the possible advantages in pigment development. In crystalline materials, the optical characteristics are not solely dependent on the molecules but also on the crystal packing;[2] it follows that the optical properties could be modified using crystal engineering techniques. We have systematically investigated co-crystallising haloanilines with dinitrobenzoic acids to build an understanding of the intermolecular interactions. Molecular disorder of one or more of the components tends to lead to layered crystal structures that include stacking interactions and therefore strong colour, indicating that molecular disorder is desirable. Defects in inorganic systems are routinely exploited as a route to enhancing or introducing physical properties but similar effects in organic systems are yet to be properly exploited. We will discuss the methods by which disorder can be designed into molecular complexes, and the local ordering effects which give rise to strong diffuse scattering. Additionally we have identified a pair of thermochromic molecular complexes, 2-iodoaniline/2-bromoaniline 3,4-dinitrobenzoic acid, where disorder appears to be crucial in lending the materials their properties. Both complexes undergo a temperature-induced colour change from red to yellow corresponding to a significant molecular rearrangement. The thermochromic transition is a single-crystal to single-crystal effect; the role of molecular disorder as a facilitator for the molecular rearrangement, maintaining the crystal integrity, will be discussed. Despite the complexes being isostructural, only the bromoaniline complex shows reversible thermochromic behaviour; subtleties in the manifestation of this disorder can explain the differences in the reversibility of the transition.

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Pyridazines in Crystal Engineering. A Systematic Evaluation of the Role of Isomerism and Steric Factors in Determining Crystal Packing and Nano/Microcrystal Morphologies

Crystal Growth & Design ◽

10.1021/cg9015383 ◽

2010 ◽

Vol 10 (6) ◽

pp. 2571-2580 ◽

Cited By ~ 16

Author(s):

Sunil Varughese ◽

Sylvia M. Draper

Keyword(s):

Crystal Engineering ◽

Crystal Packing ◽

Systematic Evaluation ◽

Steric Factors

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The Isocyanide Complexes cis-[MCl2(CNC6H4-4-X)2] (M = Pd, Pt; X = Cl, Br) as Tectons in Crystal Engineering Involving Halogen Bonds

Crystals ◽

10.3390/cryst11070799 ◽

2021 ◽

Vol 11 (7) ◽

pp. 799

Author(s):

Maria V. Kashina ◽

Daniil M. Ivanov ◽

Mikhail A. Kinzhalov

Keyword(s):

Dft Calculations ◽

Crystal Engineering ◽

Crystal Packing ◽

Noncovalent Interactions ◽

Topological Analysis ◽

Electron Localization ◽

Halogen Bonds ◽

Isocyanide Ligands ◽

1D Chains

The isocyanide complexes cis-[MCl2(CNC6H4-4-X)2] (M = Pd; X = Cl, Br; M = Pt; X = Br) form isomorphous crystal structures exhibiting the Cl/Br and Pd/Pt exchanges featuring 1D chains upon crystallisation. Crystal packing is supported by the C–X···X–C halogen bonds (HaBs), C–H···X–C hydrogen bonds (HB), X···M semicoordination, and C···C contacts between the C atoms of aryl isocyanide ligands. The results of DFT calculations and topological analysis indicate that all the above contact types belong to attractive noncovalent interactions. A projection of the electron localization function (ELF) and an inspection of the electron density (ED) and the electrostatic potential (ESP) reveal the amphiphilic nature of X atoms playing the role of HaB donors, HaB and HB acceptors, and a nucleophilic partner in X···M semicoordination.

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Crystal Engineering to Design of Solids: From Single to Multicomponent Organic Materials

Mini-Reviews in Organic Chemistry ◽

10.2174/1570193x16666190430153231 ◽

2020 ◽

Vol 17 (5) ◽

pp. 518-538

Author(s):

Andrea Mariela Araya-Sibaja ◽

Cinira Fandaruff ◽

Krissia Wilhelm ◽

José Roberto Vega-Baudrit ◽

Teodolito Guillén-Girón ◽

...

Keyword(s):

Mechanical Properties ◽

Physicochemical Properties ◽

Dissolution Rate ◽

Crystal Engineering ◽

Organic Molecules ◽

Organic Materials ◽

Crystal Packing ◽

Physical Stability ◽

Bioactive Molecules ◽

Crystal Lattices

Primarily composed of organic molecules, pharmaceutical materials, including drugs and excipients, frequently exhibit physicochemical properties that can affect the formulation, manufacturing and packing processes as well as product performance and safety. In recent years, researchers have intensively developed Crystal Engineering (CE) in an effort to reinvent bioactive molecules with well-known, approved pharmacological effects. In general, CE aims to improve the physicochemical properties without affecting their intrinsic characteristics or compromising their stability. CE involves the molecular recognition of non-covalent interactions, in which organic materials are responsible for the regular arrangement of molecules into crystal lattices. Modern CE, encompasses all manipulations that result in the alteration of crystal packing as well as methods that disrupt crystal lattices or reduce the size of crystals, or a combination of them. Nowadays, cocrystallisation has been the most explored strategy to improve solubility, dissolution rate and bioavailability of Active Pharmaceutical Ingredients (API). However, its combinatorial nature involving two or more small organic molecules, and the use of diverse crystallisation processes increase the possible outcomes. As a result, numerous organic materials can be obtained as well as several physicochemical and mechanical properties can be improved. Therefore, this review will focus on novel organic solids obtained when CE is applied including crystalline and amorphous, single and multicomponent as well as nanosized ones, that have contributed to improving not only solubility, dissolution rate, bioavailability permeability but also, chemical and physical stability and mechanical properties.

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Evaluation of fluorine-mediated intermolecular interactions in tetrafluorinated tetrahydroisoquinoline derivatives: synthesis and computational studies

Acta Crystallographica Section B Structural Science Crystal Engineering and Materials ◽

10.1107/s2052520620006873 ◽

2020 ◽

Vol 76 (4) ◽

pp. 604-617

Author(s):

Labhini Singla ◽

Hare Ram Yadav ◽

Angshuman Roy Choudhury

Keyword(s):

Intermolecular Interactions ◽

Organic Molecules ◽

Molecular Conformation ◽

Crystal Packing ◽

Weak Interactions ◽

Strong Hydrogen Bond ◽

Supramolecular Synthons ◽

Wide Range ◽

Organic Fluorine ◽

Insight Into

Intermolecular interactions involving the aromatic C—F group in the absence of other strong hydrogen bond acceptors is the theme of this article. Weak interactions involving fluorine are known to generate various supramolecular synthons, thereby altering the crystal structures of small organic molecules. It is demonstrated that the weak interactions involving organic fluorine play a major role in directing crystal packing of highly flexible organic molecules like diphenyl tetrahydroisoquinolines reported herein. The intramolecular C—H...F hydrogen bonds are found to be significant in controlling the molecular conformation in specific cases wheras the intermolecular interactions involving the C—F groups result in a wide range of supramolecular synthons involving C—H...F and C—F...F—C interactions. The interactions are studied computationally to provide insight into their energies and the topology of the interactions is studied using Atoms in Molecules. C—H...F—C interactions are found to be quite stabilizing in nature with the stabilization energy of −13.9 kcal mol−1.

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