Crystal structures of two alanylpiperidine analogues

The structure of ethyl 1-[N-(4-methylphenyl)-N-(methylsulfonyl)alanyl]piperidine-4-carboxylate, C19H28N2O5S, I, a compound of interest as activator of Ubiquitin C-terminal Hydrolase-L1 (UCH-L1), was determined by single-crystal X-ray diffraction (SCXRD) analysis. In order to find new activators, a derivative of compound I, namely, 1-[N-(4-methylphenyl)-N-(methylsulfonyl)alanyl]piperidine-4-carboxylic acid, C17H24N2O5S, II, was studied. The synthesis and crystal structure are also reported. Despite being analogues, different crystal packings are observed. Compound II bears a carboxylic group, which favors a strong hydrogen bond. A polymorph risk assessment was carried out to study interactions in compound II.

Sodium and Potassium tert-Butyl Peroxide Hydrates: Crystal Structure and Properties

Sodium and potassium tert-butyl peroxide hydrates 2Na+·2C4H9$${\text{O}}_{2}^{ - }$$·7H2O (I) and 2K+· 2C4H9$${\text{O}}_{2}^{ - }$$·4H2O (II) were prepared. According to X-ray diffraction data (CIF files CCDC no. 2081025 (I) and no. 2081024 (II)), the compounds are coordination polymers in which alkali metal atoms have C.N.(Na) of 6 or C.N.(K) of 6 and 8. The crystal packings comprise layers with clearly defined hydrophobic surfaces consisting of hydrocarbon groups and hydrophilic inner areas including water molecules, alkali metal cations, and peroxy groups of the tert-butyl peroxide anions. Compounds were characterized by vibrational spectroscopy, 1H, 13C NMR spectroscopy, thermogravimetry, and differential scanning calorimetry.

Highlighting the potential utility of MBP crystallization chaperone for Arabidopsis BIL1/BZR1 transcription factor-DNA complex

The maltose-binding protein (MBP) fusion tag is one of the most commonly utilized crystallization chaperones for proteins of interest. Recently, this MBP-mediated crystallization technique was adapted to Arabidopsis thaliana (At) BRZ-INSENSITIVE-LONG (BIL1)/BRASSINAZOLE-RESISTANT (BZR1), a member of the plant-specific BZR TFs, and revealed the first structure of AtBIL1/BZR1 in complex with target DNA. However, it is unclear how the fused MBP affects the structural features of the AtBIL1/BZR1-DNA complex. In the present study, we highlight the potential utility of the MBP crystallization chaperone by comparing it with the crystallization of unfused AtBIL1/BZR1 in complex with DNA. Furthermore, we assessed the validity of the MBP-fused AtBIL1/BZR1-DNA structure by performing detailed dissection of crystal packings and molecular dynamics (MD) simulations with the removal of the MBP chaperone. Our MD simulations define the structural basis underlying the AtBIL1/BZR1-DNA assembly and DNA binding specificity by AtBIL1/BZR1. The methodology employed in this study, the combination of MBP-mediated crystallization and MD simulation, demonstrates promising capabilities in deciphering the protein-DNA recognition code.

Halogen-Bonded BODIPY Frameworks with Tunable Optical Features

The ability to tune optical features of BODIPY materials is essential for their photo-related application. However, it is challenging to efficiently tune the crystal packing of BODIPY derivatives because of their complex nature. In this study, such control of BODIPY supramolecular assemblies was achieved by designing a BODIPY containing a halogen bond (XB) acceptor (–NO2) and donor (I, Br) to mediate halogen bonding interactions. The mono halogenated 2 and 4 was unable to form XB, whereas 3 and 5 formed isostructural mono-coordinate motif 3, 5-I (1D tubular structure) and symmetric bifurcated motif 5-II (1D zig-zag chains structure) via N-O···I,Br XB interactions. The results show that the dispersion and electrostatic component are the major source of 3, 5-I and 5-II XB formations. The XB interaction between –NO2 and X (I, Br) promote singlet-to-triplet intersystem crossing and triplet-to-singlet reverse intersystem crossing due to delocalization of oxygen electrons partially onto the Br and I. Then this interaction leads to unexpected fluorescence enhancement of 5-II. Finally, the indirect optical band gaps of the 3, 5-I and 5-II were able to be tuned in the range of 1.9–2.50 eV via XB driven crystal packings.

Halogen-Bonded BODIPY Frameworks with Tunable Optical Features

The ability to tune optical features of BODIPY materials is essential for their photo-related application. However, it is challenging to efficiently tune the crystal packing of BODIPY derivatives because of their complex nature. In this study, such control of BODIPY supramolecular assemblies was achieved by designing a BODIPY containing a halogen bond (XB) acceptor (–NO2) and donor (I, Br) to mediate halogen bonding interactions. The mono halogenated 2 and 4 was unable to form XB, whereas 3 and 5 formed isostructural mono-coordinate motif 3, 5-I (1D tubular structure) and symmetric bifurcated motif 5-II (1D zig-zag chains structure) via N-O···I,Br XB interactions. The results show that the dispersion and electrostatic component are the major source of 3, 5-I and 5-II XB formations. The XB interaction between –NO2 and X (I, Br) promote singlet-to-triplet intersystem crossing and triplet-to-singlet reverse intersystem crossing due to delocalization of oxygen electrons partially onto the Br and I. Then this interaction leads to unexpected fluorescence enhancement of 5-II. Finally, the indirect optical band gaps of the 3, 5-I and 5-II were able to be tuned in the range of 1.9–2.50 eV via XB driven crystal packings.

Existence of untypical halogen-involving interactions in crystal packings: a statistical and first-principles study

There is a common perception by the scientific community that a halogen-involving interaction forms when the distance between the donor atom and the acceptor atom is less than the sum of their van der Waals (vdW) radii.

Influence of the cis/trans configuration on the supramolecular aggregation of aryltriazoles

The ability of trans- and cis-1,2-glucopyranosyl and cyclohexyl ditriazoles, synthesized by CuAAC "click" chemistry, to form gels was studied, their physical properties determined, and the self-aggregation behavior investigated by SEM, X-ray, and EDC studies. The results revealed that self-assembly was driven mainly by π–π stacking interactions, in addition to hydrogen bonding, with the aromatic rings adopting a high degree of parallelism, as seen in crystal packings and ECD data. Furthermore, π–bromine interactions between the bromine atom of the aryl substituents and the triazole units might also contribute to an overall stabilization of the supramolecular aggregation of bis(4-bromophenyl)triazoles. The trans or cis spatial disposition of the triazole rings is highly important for gelation, with the cis configuration having higher propensity.

Halogen and Hydrogen Bonding Interplay in the Crystal Packing of Halometallocenes

This paper focuses in the influence of halogen atoms in the design and structural control of the crystal packing of Group VIII halogenated metallocenes. The study is based on the present knowledge on new types of intermolecular contacts such as halogen (X⋯X, C-X⋯H, C-X⋯π), π⋯π, and C-H⋯π interactions. The presence of novel C-H⋯M interactions is also discussed. Crystal packings are analysed after database search on this family of compounds. Results are supported by ab initio calculations on electrostatic charge distributions; Hirshfeld analysis is also used to predict the types of contacts to be expected in the molecules. Special attention is given to the competition among hydrogen and halogen interactions, mainly its influence on the nature and geometric orientations of the different supramolecular motifs. Supramolecular arrangements of halogenated metallocenes and Group IV di-halogenated bent metallocenes are also compared and discussed. Analysis supports halogen bonds as the predominant interactions in defining the crystal packing of bromine and iodine 1,1′-halometallocenes.

Quantifying intermolecular interactions for isoindole derivatives: substituent effect vs. crystal packing

The aim of the study was to examine noncovalent interactions in considerably different crystal packings of three isoindole compounds. Their structures were compared to three other closely-related derivatives described earlier in the literature. Here we discuss the crystal structures in the context of the hydrogen-bonded motifs and other weak interactions. The hierarchy of investigated intermolecular interactions was examined in a quantitative manner through pairwise interaction energies and energy framework analysis.