Crystal Molecules Research Articles

Photodimerization-Triggered Photopolymerization of Triene Coordination Polymers Enables Macroscopic Photomechanical Movements.

Controlling the packing of olefinic molecules in crystals is essential for triggering solid-state [2 + 2] photocycloaddition reactions and the synthesis of photocontrolled smart materials. Herein, we report the stepwise photodimerization-triggered photopolymerization of two triene coordination polymers (CPs), {[Zn(2-BBA)2(tpeb)]·0.5CH3CN}n (1, 2-HBBA = 2-bromobenzoic acid, tpeb = 1,3,5-tri-4-pyridyl-1,2-ethenylbenzene) and {[Zn(3-BBA)2(tpeb)]·CH3CN)}n (2, 3-HBBA = 3-bromobenzoic acid). Upon irradiation with 420 nm light, each pair of closely packed and parallel olefinic bonds in 1 undergoes a [2 + 2] cycloaddition reaction, which connects two adjacent Z-shaped chains into a ladder-like coordination chain [Zn(2-BBA)2(bpbdpvpcb)0.5]n (1a, bpbdpvpcb = 1,3-bis(4-pyridyl)-2,4-bis(3,5-di(2-(4-pyridyl)vinyl)phenyl]cyclobutene) through single-crystal to single-crystal (SCSC) transformation. After photodimerization from 1 to 1a has occurred, the olefinic bonds that were initially distant are brought in close enough proximity to meet the requirements for a subsequent [2 + 2] cycloaddition reaction. Upon further light irradiation, the neighboring bpbdpvpcb ligands in 1a experience a SCSC photopolymerization based on [2 + 2] photocycloaddition and transform into poly-3b,4,5,5a,8b,9,10a-octahydro-4,5,9,10-tetrapyridyl-2,7-di(2-(4-pyridyl)vinyl)dicyclobuta[e,l]-pyren (poly-otpdpvdcbp). 2 showed similar structural changes under UV light illumination. Under light exposure, single crystals of 1 and 2 with different morphologies exhibit bending, cracking, and jumping photomechanical motions. The composite film (1-PVA) engineered by dispersing crystalline particles of 1 in poly(vinyl alcohol) (PVA) displays interesting light-wavelength-dependent photomechanical motions and can perform photodriven swimming on a liquid surface. This work provides a useful and promising approach to enable photodimerization of those photoinactive olefin pairs embedded in CPs and opens a new route to synthesize organic polymers by using olefinic CP platforms.

Crystal structure and cryomagnetic study of a mononuclear erbium(III) oxamate inclusion complex.

The synthesis, crystal structure and magnetic properties of an oxamate-containing erbium(III) complex, namely, tetrabutylammonium aqua[N-(2,4,6-trimethylphenyl)oxamato]erbium(III)-dimethyl sulfoxide-water (1/3/1.5), (C16H36N)[Er(C11H12NO3)4(H2O)]·3C2H6OS·1.5H2O or n-Bu4N[Er(Htmpa)4(H2O)]·3DMSO·1.5H2O (1), are reported. The crystal structure of 1 reveals the occurrence of an erbium(III) ion, which is surrounded by four N-phenyl-substituted oxamate ligands and one water molecule in a nine-coordinated environment, together with one tetrabutylammonium cation acting as a counter-ion, and one water and three dimethyl sulfoxide (DMSO) molecules of crystallization. Variable-temperature static (dc) and dynamic (ac) magnetic measurements were carried out for this mononuclear complex, revealing that it behaves as a field-induced single-ion magnet (SIM) below 5.0 K.

Structural, spectral, and thermal gravimetric studies of lanthanum complexes with N,N'-tetraethyl-N''-(trichloroacetyl)phosphortriamide, 2,2'-bipyridine, and nitrate anion

Coordination compounds of lanthanum with carbacylamidophosphate – N,N'-tetraethyl-N''-(trichloroacetyl)phosphortriamide (HL) and 2,2'-bipyridine (bipy) of composition LaLbipy2(NO3)2 and LaL3bipy were synthesized and studied by means of X-ray, thermal gravimetric analyses, IR, and NMR spectroscopy. It was established that all the ligands in the complexes are coordinated towards lanthanum in bidentate manner. Coordination number of central ion equals ten and eight for LaLbipy2(NO3)2 and LaL3bipy, respectively. Coordination polyhedron of LaIII ion has distorted geometry between bicapped square antiprism and sphenocorona in LaLbipy2(NO3)2 and between square antiprism and triangular dodecahedron in LaL3bipy. The bonds lengths La–O and La–N are commensurate in the synthesized complexes. The both structures are characterized by the presence of numerous intermolecular interactions, which have been analyzed using Hirshfeld surface tool. A feature of the complex LaLbipy2(NO3)2 is the presence of two crystallographically independent molecules in crystal. The compounds LaLbipy2(NO3)2 and LaL3bipy are thermally stable to 1750С and 1650С, respectively. A feature of the tris-complex LaL3bipy is the presence of a phase transition at a temperature of 960С.

Iodo-bridged dicopper(I) complex containing a benzothienobenzothiophene unit: structure, characterization, and crystal-packing effects on solid-state photoluminescence

Abstract The title complex was newly synthesized by straightforward ligand substitution of a parent complex having a N2P2 set. The present complex had a deformed rhomboidal {Cu2I2} core with shortened Cu···Cu and prolonged I···I diagonals compared with those of the parent complex and formed one-dimensional channels filled with solvent molecules in crystals. The complex exhibited unusual red shift in solid-state photoluminescence assigned to halogen/metal-to-ligand charge transfer, indicating association of the unique crystal packing containing intramolecular electronic coupling between benzothienobenzothiophene moieties.

Anilato-Based Coordination Polymers with Slow Relaxation of the Magnetization: Role of the Synthetic Method and Anilato Ligand.

We have prepared and characterized three coordination polymers formulated as [Dy2(C6O4Cl2)3(fma)6] ⋅ 4.5fma (1) and [Dy2(C6O4X2)3(fma)6] ⋅ 4fma ⋅ 2H2O with X=Br (2) and Cl (3), where fma=formamide and C6O4X2 2-=3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone dianion with X=Cl (chloranilato) and Br (bromanilato). Compounds 1 and 3 are solvates obtained with slow and fast precipitation methods, respectively. Compounds 2 and 3 are isostructural and only differ in the X group of the anilato ligand. The three compounds present (6,3)-gon two-dimensional hexagonal honey-comb structures. Magnetic measurements indicate that the three compounds show slow relaxation of the magnetization at low temperatures when a continuous magnetic field is applied, although with different relaxation times and energy barriers depending on X and the crystallisation molecules. Compounds 1-3 represent the first examples of anilato-based lattices with formamide and field-induced slow relaxation of the magnetization.

A survey of supramolecular association involving the oxide-O atom in the crystals of triorganoamine N-oxide derivatives, RR′R″N(+)O(−)

Abstract Trimethylamine N-oxide, Me3N(+)O(−), is an important molecule in biology and medicine. Herein, a survey of the interactions involving the oxide-O atom in crystals containing derivatives of Me3N(+)O(−), namely RR′R″N(+)O(−), is presented; R,R′, R″ = alkyl and/or aryl. A total of 119 RR′R″N(+)O(−) molecules were analysed for the supramolecular interactions involving the oxide-O atom. Hydrates form the largest class of crystals, comprising over 40 % of the 91 crystals investigated, a value slightly higher than expectation. Over 80 % of molecules had at least one O–H⋯O(−)(oxide) hydrogen bond: 3, 45 and 33 % of all molecules had three, two or one O–H⋯O(−)(oxide) hydrogen bonds, respectively. Further, nearly 15 % of molecules formed at least one N–H⋯O(−)(oxide) hydrogen bond, sometimes operating in concert with O–H⋯O(−)(oxide) hydrogen bonds. The overwhelming majority of molecules featured inter- and/or intra-molecular supporting C–H⋯O(−)(oxide) contacts so that a diverse range of supramolecular interaction patterns is apparent, a situation made more complicated by the appearance of different supramolecular association patterns often observed for independent molecules in crystals with more than one molecule in the crystallographic asymmetric-unit. Of the 6 % of molecules devoid of conventional A–H⋯O(−)(oxide) hydrogen bonds, all formed three or four inter-/intra-molecular C–H⋯O(−)(oxide) contacts usually characterised by at least one short H⋯O(−)(oxide) distance.

Computational insight into the crystal structures of cubane and azacubanes.

Using quantum chemistry and atom-atom potential methods, the molecular and crystal structures of cubane 1 and all types of unsubstituted azacubanes 2-22 were calculated. Alternative possible polymorphs of cubane 1 have been proposed. The thermochemical properties of azacubanes in the gas and solid phases were assessed. Thermodynamic aspects of stability are considered, and a significant decrease in stability is revealed upon transition from cubane 1 to octaazacubane 22. It has been shown that the density and energetic properties of azacubanes depend nonlinearly on the number of nitrogen atoms in the structure and the density of octaazacubane 22 at room temperature is 1.546gcm-3, which is significantly lower than the previously given estimate. In this work, DFT calculations were conducted through the software Gaussian 09 using B3LYP functional with basis set aug-cc-PVDZ and the Grimme dispersion correction D2. For crystal structure optimization, the atom-atom potential methods with PMC (packing of molecules in crystal) program were used. Charges for molecular electrostatic potential were fitted by FitMEP, and enthalpies of formation in gas phase were assessed by G3B3.

Theoretical perspective for hydrostatic pressure responsive mechanism of room temperature phosphorescence molecules

Stimulus-responsive organic room temperature phosphorescence (RTP) materials are a class of materials that show emission property changes when subjected to diverse environmental stimuli. The change of molecular stacking modes and intermolecular interactions can result in mechanical stimulus-induced emission switching behaviour. The underlying mechanism of mechanoresponsive luminescent material is still unclear. Herein, based on density functional theory and time-dependent density functional theory calculations, the photophysical properties with response to hydrostatic pressure of RTP molecules in crystal are theoretically studied. Excited state dynamic processes are investigated by using quantum mechanics and molecular mechanics method coupled with thermal vibration correlation function method. Results show that the increase of pressure can blue-shift the RTP emissions which is mainly caused by the change of molecular conformation and the increase of bending vibration frequency. Under 2 Gpa, large spin–orbit coupling effect is determined, remarkable radiative and non-radiative decay processes are achieved. At 0.6 Gpa, a small non-radiative decay rate from T 1 to S 0 is obtained, high efficiency and long lifetime (more than 10 times the other pressures) are realised. Through further analysing the staking modes, reorganisation energies and SOC constants, relationships between molecular structures and RTP properties are determined, hydrostatic pressure responsive mechanism is revealed.

Linear furoxan assemblies incorporating nitrobifuroxan scaffold: En route to new high-performance energetic materials

Energetic materials science is undergoing a global renaissance aiming to reach an ideal combination between reliable synthetic strategies, high performance and acceptable molecular stabilities. In this work, design and synthesis of novel energetic non-hydrogen furoxan assemblies has been successfully realized. Fine tunability of molecular composition in a series of furoxan-based materials was achieved by the variation of a number of heterocyclic rings and employing N-oxide regioisomerism strategy. Using this approach, advanced energetic regioisomeric azo-bridged bifuroxan assemblies 6 and 7 as well as 3,4′-dinitro-3′,4-bifuroxan 8 with the excellent overall performance were synthesized. Calculations of Hirshfeld surfaces and molecular electrostatic potentials were conducted to better understand the relationship between the molecular structure and mechanical sensitivity in the synthesized series of energetic materials. It was found, that the supramolecular aggregation of 3,4′-dinitro-3′,4-bifuroxan 8 molecules in crystal is more anisotropic that is commonly believed to be more favorable pattern for the low sensitive substances. All target materials have high densities (1.88–1.95 g cm−3), acceptable thermal stabilities (up to 165 °C), high enthalpies of formation (1.6–2.4 kJ g−1) and positive oxygen balance to CO (up to + 25%). As a result, these compounds exhibit high detonation velocities (9.1–9.5 km s−1), excellent heats of explosion (6.6–7.2 kJ g−1) and combustion performance (Isp = 269–281 s). Therefore, these furoxan-based advanced energetic materials unveil new opportunities in search of next-generation functional organic materials for various applications.

Reactions of polyaromatic molecules in crystals under electron beam of the transmission electron microscope

Reactivity of a series of related molecules under the 80 keV electron beam have been investigated and correlated with their structures and chemical composition. Hydrogenated and halogenated derivatives of hexaazatrinaphthylene, coronene, and phthalocyanine were prepared by sublimation in vacuum to form solventless crystals then deposited onto transmission electron microscopy (TEM) grids. The transformation of the molecules in the microcrystals were triggered by an 80 keV electron beam in the TEM and studied using correlated selected area electron diffraction, conventional bright field imaging, and energy dispersive X-ray spectroscopy. The critical fluence (ē nm-2) required to cause a disappearance of the diffraction pattern was recorded and used as a measure of the reactivity of the molecules. The same electron flux (102 ē nm-2 s-1) was used throughout. Fully halogenated molecules were found to be the most stable and did not change significantly under our experimental conditions, followed by fully hydrogenated molecules with critical fluences of 104 ē nm-2. Surprisingly, semi-halogenated molecules that contained an equal number of hydrogen and halogen atoms were found to be the least stable, with critical fluences an order of magnitude lower at 103 ē nm-2. This is attributed to elimination of H-X (where X = F or Cl), followed by polymerisation of aryne / aryl radicals within the crystal. The critical fluence for the semi-fluorinated hexaazatrinaphthylene is the lowest as the presence of water molecules in its crystal lattice significantly decreased the stability of the organic molecules under the electron beam. Semi-halogenation reduces the beam stability of organic molecules compared to the parent hydrogenated molecule, thus providing the chemical guidance for design of electron beam stable materials. Understanding of molecular reactivity in the electron beam is necessary for advancement of molecular imaging and analysis methods by the TEM, molecular materials processing, and electron beam-driven synthesis of novel materials.

Unified master equation for molecules in phonon and radiation baths

We have developed a unified quantum optical master equation that includes the dissipative mechanisms of an impurity molecule in crystals. Our theory applies generally to polyatomic molecules where several vibrational modes give rise to intramolecular vibrational redistributions. The usual assumption on identical shapes of the nuclear potentials in ground and excited electronic states and the rotating wave approximation have been relaxed, i.e. the vibrational coordinates are different in the ground and excited states, with counter-rotating terms included for generality. Linear vibrational coupling to the lattice phonons accounts for dissipations via non-radiative transitions. The interaction of a molecule with photons includes Herzberg–Teller coupling as the first order non-Condon interaction where the transition dipole matrix elements depend linearly on vibrational coordinates. We obtain new cross terms as the result of mixing the terms from the zeroth-order (Condon) and first-order (non-Condon) approximations. The corresponding Lamb shifts for all Liouvilleans are derived explicitly including the contributions of counter-rotating terms. The computed absorption and emission spectra for carbon monoxide is in good agreement with experimental data. We use our unified model to obtain the spectra for nitrogen dioxide, demonstrating the capability of our theory to incorporate all typical dissipative relaxation and decoherence mechanisms for polyatomic molecules. The molecular quantum master equation is a promising theory for studying molecular quantum memory.

Synthesis and DFT analysis of non-covalent interactions in crystal structures of 6-R-2-alkoxy-, 2,3-di-, and 2,2,3-tri-tert-butylpyrrolo[1,2-b][1,2,4]triazines.

Novel 7-amino-3-tert-butyl-2-OR1-6-R2-pyrrolo[1,2-b][1,2,4]triazine-8-carbonitriles (R1 = CH2CO2Et, CH2Boc, Me, n-Bu; R2 = CO2Et, CO2n-Bu, CO2t-Bu, C6H4CO2i-Pr) have been synthesized and investigated by X-ray diffraction. Nucleophilic replacement of an alkoxy group with t-BuLi afforded sterically hindered tert-butyl 7-amino-2,3-di-tert-butyl- and 2,2,3-tri-tert-butyl-8-cyanopyrrolo[1,2-b][1,2,4]triazine-6-carboxylates. The lengths and bond angles as well as packing modes of molecules in crystals have been considered. The non-covalent interactions such as the changes in the H-bonding and close contacts were analyzed by DFT and the Hirshfeld surfaces and compared for different substituents.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11224-022-02006-x.

Boosting Efficiency of Non‐Fullerene Organic Solar Cells Via Introducing Multidimensional Second Acceptors

The active layer bulk heterojunction (BHJ) blends with a suitable phase separation and crystallization are of great importance to the exciton dissociation, charge transfer, and ultimately the efficiency of the organic solar cells (OSCs). Herein, an effective approach is developed to modulate the molecule's crystallization and phase separation of BHJ blends via introducing a multidimensional (MD) second acceptor. The efficiency of the OSCs can be largely boosted when the cross‐shaped MD acceptors are introduced into the BHJs as a third component. The ternary OSCs based on PTB7‐Th:IEICO‐4F:SFCPDT exhibit a higher power conversion efficiency (PCE) (PCE = 13.29%) than that of the PTB7‐Th:IEICO‐4F binary system (PCE = 11.67%). It is found that the ternary films deliver higher and more balanced carrier mobility, as well as reduced carrier recombination. The positive effect can be also extended to the PBDB‐T‐2F: IT‐4F‐based ternary system. When FLIDT and SFIDT are employed as the third component, the PCE values can be increased from pristine 11.98–12.42% and 13.16%, respectively. It is anticipated to further boost the efficiency of the non‐fullerene OSCs by rationally designing the structure of the third component for a state‐of‐the‐art active layer system.

Promoting a desired conformational preference of an aromatic amide in various crystals by rational design of intramolecular hydrogen bonding

Although the conformational mobility of flexible ligands provides a way to generate structural diversity in the crystalline structure, strategies are needed to promote a conformational preference based on rational design. Herein, two methoxy groups were introduced onto N,N'-bis(4-pyridyl)isophthalamide (BPI) in order to gain a conformational preference by intramolecular hydrogen bonding. Therefore, we synthesized 4,6-dimethoxy-N,N'-bis(4-pyridyl)isophthalamide (DMBPI), and further prepared organic crystals and coordination polymers of DMBPI. Single crystal X-ray diffraction revealed that all DMBPI molecules in these crystals adopt anti,anti-conformations owing to the intramolecular-hydrogen-bond formation. In contrast, the diverse conformations of BPI molecules in the 27 BPI-containing crystals are categorized into three conformation types. The remarkable difference in conformational distribution may be attributed to that the energy gaps between the different conformations of DMBPI are significantly greater than those of BPI on the basis of density functional theory calculations. These results demonstrate that introduction of a suitable substituent to form intramolecular hydrogen bonds is an effective and rational strategy for achieving an expected conformation of molecules in crystals, which may facilitate the design and controllable assembly of functional materials.

Terraced and 3D Pyramid-Shaped Polymer Single Crystal via Low Temperature-Assisted Microfluidic Technology.

3D pyramidal polymer single crystals provide spatial gradient variations within the crystal molecules, and these variations facilitate the study of the relationship between structure and properties within the molecules of various complexes with anisotropic structures. As described herein, a low-temperature-assisted microfluidic pore channeling approach is proposed to prepare structurally ordered polymer single crystals. A mixture of dichloromethane and dimethyl sulfoxide is used as a prepolymer, and a liquid microfluidic technique is employed to grow the end-functionalized polymers into 3D polymer single crystals. Through the ordered growth of single crystals, a personalized pyramidal pattern with a homogeneous structure is formed. To evaluate the mesh node density, low-temperature growth time and substrate type are also investigated. Rectangular, pyramidal, and dendritic patterns are synthesized via low-temperature single crystal growth. This work shows that low temperature-assisted microfluidics provides a novel means to tune the 3D structure of polymer single crystals.

Reversible colour/luminescence colour changes of tetracyanoruthenium(ii) complexes by sorption/desorption of water molecules in crystals

We report reversible vapochromic behaviour of tetracyanorutenium(ii) complexes by the sorption/desorption of water molecules in crystal.

Fluorenonophane chloro-benzene solvate: mol-ecular and crystal structures.

The title compound, 19 H,79 H-3,5,9,11-tetra-oxa-1,7(2,7)-difluorena-4,10(1,3)-dibenzena-cyclo-dodeca-phane-19,79-dione (fluorenonophane), exists as a solvate with chloro-benzene, C42H28O6·C6H5Cl. The fluorenonophane contains two fluorenone fragments linked by two m-substituted benzene fragments. Some decrease in its macrocyclic cavity leads to a stacking inter-action between the tricyclic fluorenone fragments. In the crystal, the fluorenonophane and chloro-benzene mol-ecules are linked by weak C-H⋯π(ring) inter-actions and C-H⋯Cl hydrogen bonds. The Cl atom of chloro-benzene does not form a halogen bond. A Hirshfeld surface analysis and two-dimensional fingerprint plots were used to analyse the inter-molecular contacts found in the crystal structure.

Charge–Transfer Fluorescence and Room-Temperature Phosphorescence from a Bisamide-Based Derivative

The development of organic luminescent materials with bimodal emissions of both fluorescence and room-temperature phosphorescent (RTP) remains a challenge. The investigation of the relationship between fluorescence and RTP performance is especially rare. In this work, we obtained an organic luminescent molecule, 1,4-phenylenebis((9H-carbazol-9-yl)methanone) (PBCM), which exhibits bimodal emissions of cyan fluorescence and yellow RTP in its crystalline state through adopting an electron donor–acceptor–donor (D–A–D) structure. The charge–transfer (CT) effects in the bimodal luminescent properties of PBCM, as well as the single-crystal structures and thermal properties, were investigated. It was found that the CT effect in the singlet states effectively reduces the ∆Est and promotes the ISC processes, resulting in an efficient phosphorescence of PBCM at room temperature. In addition, many strong intermolecular interactions are formed between the donor and acceptor parts of adjacent molecules, leading to the rigid configurations and compact packing of molecules in crystals, which was also confirmed to facilitate the efficient bimodal emissions of PBCM.

Synthesis and crystal structure of bis-[μ-N,N-bis-(2-amino-eth-yl)ethane-1,2-di-amine]-bis-[N,N-bis-(2-amino-eth-yl)ethane-1,2-di-amine]-μ4-oxido-hexa-μ3-oxido-octa-μ2-oxido-tetra-oxido-tetra-nickel(II)hexa-tantalum(V) nona-deca-hydrate.

Reaction of K8{Ta6O19}·16H2O with [Ni(tren)(H2O)Cl]Cl·H2O in different solvents led to the formation of single crystals of the title compound, [Ni4Ta6O19(C6H18N4)4]·19H2O or {[Ni2(κ4-tren)(μ-κ3-tren)]2Ta6O19}·19H2O (tren is N,N-bis-(2-amino-eth-yl)-1,2-ethanediamine, C6H18N4). In its crystal structure, one Lindqvist-type anion {Ta6O19}8- (point group symmetry ) is connected to two NiII cations, with both of them coordinated by one tren ligand into discrete units. Both NiII cations are sixfold coordinated by O atoms of the anion and N atoms of the organic ligand, resulting in slightly distorted [NiON5] octa-hedra for one and [NiO3N3] octa-hedra for the other cation. These clusters are linked by inter-molecular O-H⋯O and N-H⋯O hydrogen bonding involving water mol-ecules into layers parallel to the bc plane. Some of these water mol-ecules are positionally disordered and were refined using a split model. Powder X-ray diffraction revealed that a pure crystalline phase was obtained but that on storage at room-temperature this compound decomposed because of the loss of crystal water mol-ecules.

Band-gap-tailoring in Liquid Crystals: Organizing Metal Atoms and Nanoclusters in LC Media

ABSTRACT In this paper, we have studied a set of eleven liquid crystal (LC) molecules and focused on investigating their properties such as polarisability, entropy, dipole moment, thermal and electrical energy, specific heat capacity, band gap, etc. The variations due to doping metals atoms and their clusters have been verified by quantifying physical observables using IR, UV and NMR spectra of these compounds least known and understood experimentally. The reactivities and the stabilities of the molecules are explored using calculations such as HOMO-LUMO structures, HOMO-LUMO gap based on density functional theory. We have used DFT calculations with B3LYP/6-311 G (d, p) and LanL2DZ basis sets. The investigations have been carried out for LCs including 4-Cyano-4ʹ-pentyl-bi-phenyl (5CB), sterols, organometallic LCs, heterocyclic LCs, etc. The observations are focused on the formation of nanodots by nucleation process linked to the LCs. We have also verified the persistence of the liquid crystalline phase after binding metal atoms and nanodots via XRD spectra obtained using VESTA Software. Coupling of nanodots has also been reported in this paper obtained and analysed using Spartan18 Software. We have uniquely defined and used a new method to obtain band gaps in these LCs using UV-vis spectra and compared with those obtained from HOMO-LUMO concept.