Network Formation via Anion Coordination: Crystal Structures Based on the Interplay of Non-Covalent Interactions.
ABSTRACT: We describe the synthesis and the structural characterization of new H?L(CF?CO?)? (1) and H?L(Ph?PO?)? (2) compounds containing the diprotonated form (H?L2+) of the tetrazine-based molecule 3,6-di(pyridin-4-yl)-1,2,4,5-tetrazine. X-ray diffraction (XRD) analysis of single crystals of these compounds showed that H?L2+ displays similar binding properties toward both anions when salt bridge interactions are taken into account. Nevertheless, the different shapes, sizes and functionalities of trifluoroacetate and diphenyl phosphate anions define quite different organization patterns leading to the peculiar crystal lattices of 1 and 2. These three-dimensional (3D) architectures are self-assembled by a variety of non-covalent forces, among which prominent roles are played by fluorine-? (in 1) and anion-? (in 2) interactions.
Project description:Herein we disclose the synthesis and full characterization of the first monocyclic aromatic 1,2,3,5-tetrazine, 4,6-diphenyl-1,2,3,5-tetrazine. Initial studies of its cycloaddition reactivity, mode, regioselectivity, and scope illustrate that it participates as the 4?-component of well-behaved inverse electron demand Diels-Alder reactions where it preferentially reacts with electron-rich or strained dienophiles. It was found to exhibit an intrinsic reactivity comparable to that of the isomeric 3,6-diphenyl-1,2,4,5-tetrazine, display a single mode of cycloaddition with reaction only across C4/N1 (no N2/N5 cycloaddition observed), proceed with a predictable regioselectivity (dienophile most electron-rich atom attaches to C4), and manifest additional reactivity complementary to the isomeric 1,2,4,5-tetrazines. It not only exhibits a remarkable cycloaddition reactivity, surprisingly good stability (e.g., stable to chromatography, long-term storage, presence of H2O even as reaction co-solvent), and broad cycloaddition scope, but it also displays powerful orthogonal reactivity with the 1,2,4,5-tetrazines. Whereas the latter reacts at extraordinary cycloaddition rates with strained dienophiles (tetrazine ligation), the new and isomeric 1,2,3,5-tetrazine displays similarly remarkable cycloaddition rates and efficiencies with amidines (1,2,3,5-tetrazine/amidine ligation). The crossover reactivities (1,2,4,5-tetrazines with amidines and 1,2,3,5-tetrazines with strained dienophiles) are sufficiently low to indicate they may be capable of use concurrently without competitive reactions.
Project description:The asymmetric unit of the title 1:1 adduct, C(10)H(8)N(2)S·C(6)F(4)I(2), comprises a half-mol-ecule of 1,2,4,5-tetra-fluoro-3,6-diiodo-benzene, and half a 4-(pyridin-4-ylsulfan-yl)pyridine mol-ecule. The former is completed by crystallographic inversion symmetry, the latter by twofold symmetry, with the S atom lying on the rotation axis. The almost planar 1,2,4,5-tetra-fluoro-3,6-diiodo-benzene mol-ecule (r.m.s. deviation of all 12 atoms = 0.016?Å) and twisted 4-(pyridin-4-ylsulfan-yl)pyridine mol-ecule [dihedral angle between pyridyl rings = 54.88?(13)°] are connected by N?I inter-actions [2.838?(4)?Å], generating a supra-molecular chain with a step-ladder topology. These chains are connected in the crystal by C-H?F and C-H??(pyrid-yl) inter-actions.
Project description:Herein, we report the synthesis of a novel, tetrazine-based conjugated polymer. Tetrazines have the benefit of being strong electron acceptors, while little steric hindrance is imposed on the flanking thiophene rings. Conversion of a suitably substituted nitrile precursor led to 3,6-bis(5-bromo-4-(2-octyldodecyl)thiophen-2-yl)-1,2,4,5-tetrazine (2OD-TTz). Palladium-catalyzed copolymerization of 2OD-TTz with a bithiophene monomer yielded an alternating tetrazine-quaterthiophene copolymer (PTz4T-2OD). The polymer PTz4T-2OD showed an optical band gap of 1.8 eV, a deep HOMO energy level of - 5.58 eV and good solubility. In combination with the non-fullerene acceptor ITIC-F, solar cells with power conversion efficiencies of up to 2.6% were obtained.
Project description:In the present work we have calculated several DFT reactivity descriptors for 1,2,4,5-Tetrazine at the B3LYP/6-311++G(d,p) level of theory in order to analyze its reactivity in vacuum and solvent phases. Whereas, the influence of the solvent was taken into account employing the PCM model. DFT-based descriptors such as (electronic chemical potential, electrophilicity, condensed Fukui function….) have been determined to predict the reactivity of 1,2,4,5-Tetrazine. A series of eighteen 1,2,4,5-Tetrazine derivatives was studied by using two computational techniques, namely, quantitative structure activity relationship (QSAR) and molecular docking. QSAR models of the antitumor activity of some 1,2,4,5-Tetrazine derivatives were established in gas and solvent phases which exhibited good statistical values for both cases. Whereas, multiple linear regression (MLR) procedure was used to obtain the best QSAR models and the leave-one-out (LOO) method to estimate the predictivity of our models. The most and the least active compounds were docked with the protein (3C4E) to confirm those obtained results from QSAR models and elucidate the binding mode between this type of compounds and corresponding protein.
Project description:The structure of the title compound, C12H10N6, at 100?K has monoclinic (P21/n) symmetry. Crystals were obtained as a yellow solid by reduction of 3,6-bis-(pyridin-2-yl)-1,2,4,5-tetra-zine. The structure displays inter-molecular hydrogen bonding of the N-H?N type, ordering mol-ecules into infinite ribbons extending along the  direction.
Project description:Hydrogen bonding is an important noncovalent interaction that plays a key role in most of the CHNO-based energetic materials, which has a great impact on the structural, stability, and vibrational properties. By analyzing the structural changes, IR spectra, and the Hirshfeld surfaces, we investigated the high-pressure behavior of 3,6-dihydrazino-s-tetrazine (DHT) to provide detailed description of hydrogen bonding interactions using dispersion-corrected density functional theory. The strengthening of hydrogen bonding is observed by the pressure-induced weakening of covalent N-H bonds, which is consistent with the red shift of NH/NH2 stretching vibrational modes. The intermolecular interactions in DHT crystals lead to more compact and stable structures that can increase the density but diminish the heat of detonation, Q. The calculated detonation properties of DHT (D = 7.62 km/s, P = 25.19 GPa) are slightly smaller than those of a similar explosive 3,6-bis-nitroguanyl-1,2,4,5-tetrazine (D = 7.9 km/s, P = 27.36 GPa). Overall, the crystallographic and spectroscopic results along with Hirshfeld surface analysis as a function of pressure reveal the presence of strong hydrogen bonding networks in the crystal structure of DHT.
Project description:Functionalized O6-coronaarenetetrazines were synthesized efficiently and conveniently by means of a macrocyclic condensation reaction between N-functionalized 3,6-dihydroxyphthalimides and 3,6-dichlorotetrazine under mild conditions in a one-pot reaction manner. The novel macrocycles exist as a mixture of rapidly interconvertible conformers in solution while in the solid state they adopt the conformation in which three phthalimide units are cis,trans-orientated. Acting as electron-deficient macrocyclic hosts, the synthesized O6-coronaarenetetrazines self-regulated conformational structures to complex anions in the gas phase and in the solid state owing to the anion-π noncovalent interactions between anions and the tetrazine rings.
Project description:Photocleavable hydrogels are of great importance in the field of controlled drug delivery, stem cell fate regulation, surface patterning, and intelligent devices. However, the development of novel photocleavable gel systems by visible light is usually met with challenges such as the lack of efficient and tunable photocleavable groups and reactions. Herein, we reported the facile fabrication of a new type of photocleavable hydrogels by the direct gelation of 4-arm thiol-terminated polyethylene glycol with 3,6-dichloro-1,2,4,5-tetrazine via the formation of S,S-tetrazine linkages. The prepared hydrogels underwent efficient degradation upon irradiation by ultraviolet or green light, and the degradation kinetics could be significantly promoted by hydrogen peroxide. Correspondingly, the hydrogels loaded with calcium peroxide microparticles or glucose oxidase/catalase enzymes enabled the precise and efficient in vivo photocontrol of gel degradation and drug release for cancer treatment. This work offers a promising and facile strategy towards the fabrication of visible light cleavable hydrogels with tunable and on-demand drug release properties.
Project description:The properties as well as solid-state structures, singlet fission, and organic field-effect transistor (OFET) performance of three tetrafluoropentacenes (1,4,8,11: 10, 1,4,9,10: 11, 2,3,9,10: 12) are compared herein. The novel compounds?10 and 11 were synthesized in high purity from the corresponding 6,13-etheno-bridged precursors by reaction with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate at elevated temperatures. Although most of the molecular properties of the compounds are similar, their chemical reactivity and crystal structures differ considerably. Isomer?10 undergoes the orbital symmetry forbidden thermal [4+4] dimerization, whereas 11 and 12 are much less reactive. The isomers 11 and 12 crystallize in a herringbone motif, but 10 prefers ?-? stacking. Although the energy of the first electric dipole-allowed optical transition varies only within 370?cm-1 (0.05?eV) for the neutral compounds, this amounts to roughly 1600?cm-1 (0.20?eV) for radical cations and 1300?cm-1 (0.16?eV) for dications. Transient spectroscopy of films of 11 and 12 reveals singlet-fission time constants (91±11, 73±3?fs, respectively) that are shorter than for pentacene (112±9?fs). OFET devices constructed from 11 and 12 show close to ideal thin-film transistor (TFT) characteristics with electron mobilities of 2×10-3 and 6×10-2 ?cm2 ?V-1 ?s-1 , respectively.
Project description:The polymeric title compound, poly[aqua-hemi[?2-3,6-bis-(pyrimidin-2-yl)-1,4-di-hydro-1,2,4,5-tetra-zine](?3-sulfato)-cadmium(II)], [Cd(SO4)(C10H8N8)0.5(H2O)] n , (I), represents an example of a three-dimensional coordination polymer resulting from the reaction of CdSO4·8/3H2O with 3,6-bis-(pyrimidin-2-yl)-1,4-di-hydro-1,2,4,5-tetra-zine (H2bmtz, C10H8N8) under hydro-thermal conditions. The CdII atom has a distorted octa-hedral coordination environment defined by two nitro-gen atoms from one H2bmtz ligand, three oxygen atoms from three different sulfate anions, and one oxygen atom from a coordinating water mol-ecule. The 1,4-di-hydro-1,2,4,5-tetra-zine ring of the H2bmtz ligand is located about an inversion center, with the NH group being equally disordered over two sites. The sulfate anion acts as a ?3-bridging ligand to connect three CdII atoms, resulting in the formation of [Cd(SO4)(H2O)] sheets propagating parallel to the bc plane. Adjacent sheets are inter-connected across the H2bmtz ligands, which coordinate the CdII atoms in a bis-bidentate coordination mode, to form a three-dimensional framework structure. The framework is further stabilized by classical O-H?O hydrogen bonds involving the coordinating water mol-ecules and the sulfate groups, and by N-H?O hydrogen bonds between the disordered tetra-zine NH groups and sulfate oxygen atom, along with C-H?? and ?-? stacking [centroid-to-centroid separation = 3.5954?(15)?Å] inter-actions between parallel pyrimidine rings of the H2bmtz ligand.