Single-crystal X-ray Structure Analysis Research Articles

Tetradentate Pt(II) Complexes Based on Xylenylamino Linked Dual Pyrazolate Chelates for Organic Light Emitting Diodes.

In this work, we report the syntheses of three Pt(II) emitters, namely, Pt4N1, Pt4N2, and Pt4N3, to which their tetradentate chelates were assembled by linking two pyrazolate chelates with a single xylenylamino entity. Functionalization of Pt4N1 was achieved upon the addition of electronegative CF3 substituent on pyridinyl groups and switching to more electron-deficient pyrazinyl groups in giving Pt4N2 and Pt4N3, respectively. The vertically arranged xylenylamino entity has effectively suppressed the inter-molecular π-π stacking and Pt⋅⋅⋅Pt interaction, as shown by the single crystal X-ray structural analyses. Upon fabrication of OLED devices, Pt4N2 and Pt4N3 based devices delivered efficient cyan and green emission, with an EQEmax of 15.2 % and 11.2 %, respectively, affirming the successfulness of the tetradentate chelating strategy.

Meta-substituted thienoviologen with enhanced radical stability via π-π interaction modulation for neutral aqueous organic flow batteries

The aqueous organic redox flow batteries (AORFBs) are recognized as the most promising large-scale storage technology for long-duration energy storage (LDES). Although viologen derivatives are widely used as anolyte materials for AORFBs, their practical application is strongly limited by weak conjugation and unstable radicals. Here, we present a novel thienoviologen derivative, [(NPr)2SV]Cl4, achieved utilizing a meta-substitution approach based on the pristine viologen derivatives ( [(NPr)2V]Cl4). Compared to other ortho- and para-substitution methods, this strategy features a locked plane configuration (0.14°), effectively regulating π-π interactions and suppressing reactivity between radical and oxygen, which is confirmed via X-ray single-crystal structural analyses, spectroscopy techniques, molecular dynamics simulation accompanied by linear ion trap mass spectrometry experiments. Additionally, the meta-substituted [(NPr)2SV]Cl4 significantly improves water solubility (2.39 M), enhances aromaticity, and extends radical lifetime compared with para-substituted [(NPr)2TV]Cl4. Consequently, the cycling stability of the [(NPr)2SV]Cl4-based AORFB over 2500 cycles is 4.1 times higher than that of [(NPr)2TV]Cl4. Furthermore, the 0.5 M battery delivers an impressive 99.83% capacity retention during 200 cycles and a power density of 147 mW cm-2.

Synthesis and Analysis of (γ,γ',γ''-Trifluoro)neopentyl (TFNP) Aryl Ethers as a Polar Fluoroaliphatic Motif.

A route is developed to (γ,γ',γ'''-trifluoro)neopentyl (TFNP) aryl ethers to extend the methods for the introduction of the tert-butyl group, carrying a fluorine on each of the methyl substituents. The route combines neopentyltosylate 3 with phenols and thiophenols to give efficient substitution reactions to the corresponding TFNP aryl ethers. The three C-F bonds adopt a helical propeller conformation as revealed by computation and single crystal X-ray structure analysis. The LogPs of TFNP ethers are lower (more hydrophilic) than their neopentyl analogues. The metabolism of selected TFNP ethers was explored in the fungus Cunninghamella elegans.

Monitoring the Dissolution Behavior of Novel Pharmaceutical Cocrystals Consisting of Antimalarial Drug Artemisinin with Probe-Type Low-Frequency Raman Spectrometer

Artemisinin (ART) is a most promising antimalarial agent. However, its low aqueous solubility limits its oral absorption, resulting in low bioavailability. In this study, we have successfully discovered a novel cocrystal with 2-methyl resorcinol (ART-2MRE) providing improved solubility compared with a previously reported cocrystal with resorcinol (ART-RES). Single crystal X-ray structure analysis revealed that the ART-2MRE cocrystal was composed of ART and 2MRE in a molar ratio of 2 : 1. Though the ART-2MRE and ART-RES cocrystals were found to have similarities in their crystal structures, with one layer of a cocrystal former and two layers of ART arranged in alternating rows, the ART-2MRE cocrystal showed higher dissolution rate than ART-RES cocrystal. In situ real-time low-frequency (LF) Raman monitoring and powder X-ray diffraction (PXRD) measurements of the crystals during the dissolution test proved useful to investigate the dissolution behavior of the cocrystals. Low-frequency Raman monitoring revealed that as dissolution progressed, there was a continuous shift from the peak unique to the ART-2MRE cocrystal to the peak unique to the ART stable form. Similar observations were obtained in PXRD measurements as well. Furthermore, experiments were conducted by adding a polymer to the dissolution test solution to investigate the dissolution behavior under supersaturation, indicating the possibility of differences in the dissolution behavior between the ART-2MRE cocrystal and ART-RES cocrystal. Understanding the dissolution behavior from cocrystals is essential in developing cocrystals.

Machine Learning-Inspired Molecular Design, Divergent Syntheses, and X-Ray Analyses of Dithienobenzothiazole-Based Semiconductors Controlled by S⋅⋅⋅N and S⋅⋅⋅S Interactions.

Inspired by the previous machine-learning study that the number of hydrogen-bonding acceptor (NHBA) is important index for the hole mobility of organic semiconductors, seven dithienobenzothiazole (DBT) derivatives 1 a-g (NHBA=5) were designed and synthesized by one-step functionalization from a common precursor. X-ray single-crystal structural analyses confirmed that the molecular arrangements of 1b (the diethyl and ethylthienyl derivative) and 1c (the di(n-propyl) and n-propylthienyl derivative) in the crystal are classified into brickwork structures with multidirectional intermolecular charge-transfer integrals, as a result of incorporation of multiple hydrogen-bond acceptors. The solution-processed top-gate bottom-contact devices of 1b and 1c had hole mobilities of 0.16 and 0.029 cm2 V-1s-1, respectively.

A stable 2D Cd (II) coordination polymer based on mixed ligands as a fluorescence sensor for detection of tetracycline antibiotic in milk and honey

An innovative two-dimensional Cd (II) coordination polymer, namely, [Cd(L)(dibp)] (CP 1) (dibp= 4,4′-di(1H-imidazol-1-yl)-1,1′-biphenyl; H2L= 5-(1-oxoisoindolin-2-yl)isophthalic acid), have been successfully synthesized under solvothermal condition and characterized by X-ray single crystal diffraction, PXRD, IR, TGA, elemental analysis and solid-state fluorescence analysis. Single-crystal X-ray structural analysis suggests that CP 1 crystallizes in monoclinic system with a space group of P21/c and displays a 2D layer based on centrosymmetric binuclear [Cd2(CO2)4N4] units. Sensing experiments have shown that CP 1, as an emerging fluorescent sensor, can selectively, sensitively and quickly detect Tetracycline antibiotic (TC) with fantastic reusability and low detection limit (LOD = 0.092 μM). At the same time, the fluorescence quenching mechanism of CP 1 may be the FRET and PET. Excitingly, CP 1 as a novel fluorescent sensor can detect TC in milk and honey with recovery rates of 96.8–101.2 % and 97.2–100.8 %, respectively.

Synthesis of base-modified fluorescent furo[3,2-c]coumarin nucleosides and their photophysical studies

A small library of fluorescent furo[3,2-c]coumarin nucleoside analogues has been successfully synthesized via a one-pot condensation reaction of 3′,5′-di-O-acetyl-5-formyl-2′-deoxyuridine, alkyl isocyanides, and differently substituted 4-hydroxycoumarins in acetonitrile at 80 °C. Further, the synthesized compounds have been characterized by IR, 1H NMR, 13C NMR, 1H–1H COSY, 1H–13C HETCOR, 2D NOESY NMR experiments, HRMS measurements and single crystal X-ray structure analysis of compound 5-(2′'-N-(cyclohexyl)-amino-4′'H-furo[3,2-c]chromen-4-one-3′'-yl)-2′-deoxyuridine. The electronic structure of these modified nucleosides has been examined by Density Functional Theory (DFT). The synthesized nucleoside analogues exhibited a prominent emission spectrum, featuring a band around 500 nm (with excitation at 380 nm). Photophysical investigations revealed a noteworthy fluorescence intensity, along with excellent Stokes shift values (54–194 nm) and higher quantum yields (0.010–0.515) in comparison to other pyrimidine-based fluorescent nucleosides. The solvatochromic studies of 5-(2′'-N-(cyclohexyl)-amino-8′'‑chloro-4′'H-furo[3,2-c]chromen-4-one-3′'-yl)-2′-deoxyuridine determined the quantum yield (ΦF) to be 0.515 in DMSO (λabs = 388 nm). This emphasizes the potential utility of these modified nucleosides in probing the local structure and dynamics of nucleic acids. Moreover, the scalability of the synthesis protocol was effectively demonstrated by producing one of the compounds on a gram scale, exhibiting its practical viability for large-scale production.

Design and synthesis of two new thiosemicarbazide based Schiff base metal complexes of nickel (II): DNA binding study and cytotoxicity profile analysis

Two new nickel (II) substituted thiosemicarbazone Schiff base complexes [Ni(meph)2] (1) [where H2meph = (2E)-N-methyl-2-[1-(pyridin-2-yl)ethylidene]hydrazine-1-carbothioamide] and [Ni(hmm)2](NO3)2·2H2O (2) [where H2hmm = (2E)-2-[(2-hydroxyphenyl)methylidene]-N-methylhydrazine-1-carbothioamide] have been designed and synthesized by the condensation of 4-methyl-3-thiosemicarbazide with 2-acetylpyridine and salicylaldehyde respectively. Both the metal complexes 1 and 2 are characterized using different available spectroscopic techniques like FT-IR, UV–Vis spectroscopy, elemental analysis, and single crystal X-ray structure analysis. X-ray crystal structure analysis reveal that complex 1 and 2 are octahedral Ni(II) complexes. The calf-thymus CT-DNA-binding property of 1 and 2 has been evaluated by employing UV–Vis and fluorescence spectral titration. All the results show that CT-DNA binds with both nickel(II) complexes 1 and 2. In vitro cytotoxicity activity of complexes 1 and 2 toward A375 and MDA-MB-231 was evaluated using MTT assay and other methods which confirm that both complexes 1 and 2 behave as promising anti-cancer agents.

Two-Coordinate Dinuclear Donor-Gold(I)-Acceptor Complexes Exhibiting Multiple Excitation Wavelength Dependent Phosphorescence.

Two-coordinate Au(I) complexes with a donor-metal-acceptor (D-M-A) structure have shown rich luminescent properties. However, charge-neutral dinuclear donor-metal-acceptor type Au(I) complexes featuring aurophilic interactions have been seldom explored. Herein, we describe the structures and photoluminescence properties of two dinuclear Au(I) complexes, namely DiAu-Ph and DiAu-Me. Single crystal X-ray structural analysis of DiAu-Ph reveals a short intramolecular Au-Au distance of 3.224 Å. In dilute solution and doped films, excitation wavelength dependent multiple phosphorescence phenomena were observed for these dinuclear complexes. Theoretical calculations reveal that the aurophilic interaction causes increased contribution of the Au d orbital to the highest occupied molecular orbitals. Thus, the gap between singlet and triplet excited states (ΔEST) is enlarged, which disables the thermally activated delayed fluorescence (TADF). Moreover, the large energy separation (0.45-0.52 eV) and the different orbital configurations between the various excited states result in an inefficient internal conversion, accounting for their multiple phosphorescence properties.

All-Calixarene-Protected Silver Nanocluster with All Silver Atoms in a Face-Centered Cubic Arrangement.

Tailoring the surface ligands of metal nanoclusters is important for engineering unique configurations of metal nanoclusters. Thiacalix[4]arene has found extensive applications in the construction of metal nanoclusters. In this investigation, we present the synthesis and characterization of the first all-calixarene-protected silver nanoclusters, [Ag(CH3CN)4]2[Ag44(BTCA)6] (Ag44, H4BTCA = p-tert-butylthiacalix[4]arene). Single-crystal X-ray structural analysis reveals that all silver atoms are in a face-centered cubic (fcc) arrangement. The formation of such an fcc structure is attributed to the selectively passivation on {100} facets by BTCA4-. Thiacalixarene substantially facilitates the stability of Ag44 due to its multiple coordination sites and bulkiness. Mass spectrometry and theoretical calculations reveal that Ag44 is a superatomic silver nanocluster with 22 free electrons in the following configuration: 1S21P61D61F22S21D4. This work not only elucidates the impact of macrocyclic ligands on the stabilization of silver clusters but also furnishes an approach for assembling atomically precise fcc nanoclusters.

Interplay of kernel shape and surface structure for NIR luminescence in atomically precise gold nanorods

It is challenging to attain strong near-infrared (NIR) emissive gold nanoclusters. Here we show a rod-shaped cluster with the composition of [Au28(p-MBT)14(Hdppa)3](SO3CF3)2 (1 for short, Hdppa is N,N-bis(diphenylphosphino)amine, p-MBT is 4-methylbenzenethiolate) has been synthesized. Single crystal X-ray structural analysis reveals that it has a rod-like face-centered cubic (fcc) Au22 kernel built from two interpenetrating bicapped cuboctahedral Au15 units. 1 features NIR luminescence with an emission maximum at 920 nm, and the photoluminescence quantum yield (PLQY) is 12%, which is 30-fold of [Au21(m-MBT)12(Hdppa)2]SO3CF3 (2, m-MBT is 3-methylbenzenethiolate) with a similar composition and 60-fold of Au30S(S‑t‑Bu)18 with a similar structure. time-dependent DFT(TDDFT)calculations reveal that the luminescence of 1 is associated with the Au22 kernel. The small Stokes shift of 1 indicates that it has a very small excited state structural distortion, leading to high radiative decay rate (kr) probability. The emission of cluster 1 is a mixture of phosphorescence and thermally activated delayed fluorescence(TADF), and the enhancement of the NIR emission is mainly due to the promotion of kr rather than the inhibition of knr. This work demonstrates that the metal kernel and the surface structure are both very important for cluster-based NIR luminescence materials.

Synthesis, structure, characterization and one pot catalytic activity of half-sandwich iridium(III) complexes

A series of stable mononuclear half-sandwich iridium(III) complexes of the general formula [(η5-C5Me5)Ir(L)Cl](BPh4) has been synthesized in dry methanol using different imino pyridine ligands (L1–L6) and [(η5-C5Me5)2Ir2(µ-Cl)2Cl2] in a 2:1 molar ratio. All complexes were fully characterized by melting point, CHN analysis, FT-IR, UV–visible, 1H NMR, 13C NMR spectroscopy and mass spectrometry. The structure of complex 3 [(η5-C5Me5)Ir(L3)Cl](BPh4) was determined by single crystal X-ray structure analysis, showing a chelating coordination mode of the imino pyridine L3. One pot organic transformations of aldehyde to amide were carried out by complexes 1–6 in toluene at 110 °C in the presence of hydroxyl amine hydrochloride and sodium bicarbonate. The catalytic activity of complex 3 was found to be excellent, showing high conversion with catalytic turnover frequency up to 500.

In-silico antibacterial activity of piperazinyl-based copper(II) metallo-organic pharmacophores

The piperazinyl-based Cu(II)-Schiff base complex {[Cu(HL1′)(N3)]2∙(ClO4)2·4H2O} (1) [HL1′ is the Zwitter ionic form of (E)-2-((2-piperazin-1-ylethylimino)methyl)phenol] was synthesized and characterized by spectroscopic and single crystal X-ray diffraction studies. The X-ray single crystal structure analysis shows that the asymmetric unit of 1 contains a four-coordinate discrete complex cation, [Cu(HL1′)(N3)]+ (1a), with a perchlorate anion and a lattice water molecule. Two square planar units of 1a are dimerized by weak Cu···N intermolecular interaction, forming [Cu(HL1′)(N3)]2 2+ (1′a). DFT and TD-DFT calculations of the monomeric cationic unit, [Cu(HL1′)(N3)]+ (1a) were performed. In-silico antibacterial activities of HL1 as well as monomeric and dimeric cationic units 1a and 1'a, respectively, were performed and study shows that 1a (EC50 0.30 μM) and 1′a (EC50 0.06 μM) may be treated as antibacterial drugs after in-vivo analysis and clinical testing.

Dual Emission with Efficient Phosphorescence Promoted by Intermolecular Halogen Interactions in Luminescent Tetranuclear Zinc(II) Clusters.

The development of Zn-based phosphorescent materials, associated with a ligand-centered (LC) transition, is extremely limited. Herein, we demonstrated dual emissions including fluorescence and phosphorescence in luminescent tetranuclear Zn(II) clusters [Zn4LI4(μ3-OMe)2X2] (HLI = methyl-5-iode-3-methoxysalicylate; X = I, Br, Cl), incorporating iodine-substituted ligands. Single-crystal X-ray structural analyses and variable-temperature emission spectra studies revealed the presence of iodine substitutions, and intermolecular halogen interactions produced the internal/external heavy-atom effects and yielded strong green phosphorescence with a long emission lifetime (λmax = 510-522 nm, Φem = 0.28-0.47, τav = 0.78-0.95 ms, at 77 K). This work provided a new example that the introduction of halogen interactions is an advantageous approach for inducing phosphorescence in fluorescent metal complexes.

Layer-Ordered Organooxotin Clusters for Extreme-Ultraviolet Photolithography.

Extreme-ultraviolet (EUV) photolithography, which enables the high-throughput production of well-defined patterns with critical dimensions on the scale of several nanometers, is essential for the fabrication of a highly integrated semiconductor. The full exploitation of EUV lithographic techniques necessitates the development of photoresist (PR) materials with both high EUV sensitivity and a long shelf-life. However, despite notable advances, the available library of EUV PR materials remains limited. Here we report EUV PRs capable of forming preorganized layers consisting of ladder-structured tetranuclear stannoxanes. Single-crystal X-ray structure analyses reveal a close interlayer distance of 8.5 Å through interdigitation of the pseudoaxial butyl chains. The developed EUV PR materials exhibit high solubility in organic solvents commonly used in semiconductor processing, enabling the preparation of PR solutions with superior wettability and uniform film-forming ability on Si wafer substrates. These PR solutions also demonstrate notable resistance to hydrolytic decomposition for as long as 1 month, indicating a long shelf-life. Our PR materials enabled negative-tone patterning processes that involved a solubility decrease upon irradiation. The presence of chromophoric ligands makes our PR materials compatible with conventional UV photolithography, through photochemical reactions involving carbonyl units. In addition, e-beam and EUV lithography could produce fine line patterns of our PRs, with critical dimensions of 20 and 15 nm, respectively. Our research showcases the potential of layer-ordered organooxotin clusters for EUV PR applications.

Synthesis and Properties of Cyclic π-Conjugated Molecules and Their Dication and Monoradical Cation.

We synthesized cyclic π-conjugated molecules by double Friedel-Crafts reaction of amino group-substituted 1,2-bis(2-phenylethynyl)benzene with Meldrum's acid derivative. The structures of the cyclic π-conjugated molecules were determined by single-crystal X-ray structure analysis. The oxidation of the dimethylamino group-substituted π-conjugated molecule with NOBF4 gave a closed-shell dication that is stable at >210 °C. The monoradical cation of the di(4-methoxyphenyl)amino group-substituted π-conjugated molecule is stable in dichloromethane solution (half-life of nearly 15 days) and shows near-infrared absorption.

Trickier than It Looks: Isomerization between Five- and Six-Coordinated Zinc in Heterometallic Li2Zn2 Molecule.

This report describes the synthesis and characterization of two heterobimetallic Li-Zn coordination isomers [Li2Zn2(tbaoac)6] (tbaoac = tert-butyl acetoacetato) that have been isolated separately by the same stoichiometric reaction run in different organic solvents. The 6-coordinated zinc isomer (6-Zn) was synthesized in acetone with high yield, while the 5-coordinated one (5-Zn) was readily obtained from ethanol. The 5-Zn isomer has a low solubility in organic solvents such as alkanes and haloalkanes, while its 6-Zn counterpart exhibits a good solubility in almost all common solvents. Two isomeric molecules feature similar centrosymmetric tetranuclear cyclic assemblies, which are different in their arrangement of tbaoac ligands. While all ligands act as μ2-type in the structure of 5-Zn, the two tbaoac groups chelating Li appear as μ3-type in 6-Zn, thus providing an additional coordination for Zn ions. However, the real structural transformation between these isomers was shown to be more complex than simply making or breaking a couple of Zn-O bonds. X-ray single-crystal structure analysis, powder X-ray diffraction, multinuclear NMR, DART mass spectrometry, ICP-OES analysis, and TGA have been employed for the characterization of the isomers. The combination of powder X-ray diffraction and 1H NMR investigation revealed that 6-Zn isomer can be quantitatively transformed to 5-Zn in ethanol, while the reverse conversion instantly takes place in acetone.

Optical Property Control by the Interligand Charge Transfer Excited State in Brominated Homoleptic and Heteroleptic Aluminum Dinuclear Triple-Stranded Helicates.

The utilization of aluminum, an abundant and inexpensive element, for the synthesis of novel functional complexes is extremely important, but the design and control of photofunctionality are still unexplored. In this study, we focused on our previously developed dinuclear triple-stranded helicates incorporating two aluminum ions (ALPHY) to synthesize both homoleptic and heteroleptic complexes with bromine atoms at the 3-position of the pyrrole moiety in the Schiff base ligands. The brominated Schiff base ligands were reacted with AlCl3 to synthesize homoleptic complexes, while different ligands were mixed to prepare heteroleptic complexes. Single-crystal X-ray structural analysis revealed the structures of these novel complexes. We found that increasing the degree of bromination resulted in a tunable emission color, shifting progressively from 550 (yellow) to 566 nm (orange). Optical resolution of the complexes facilitated the observation of mirror-image circular dichroism and circularly polarized luminescence. Furthermore, employing ultrafast spectroscopy techniques, we have elucidated that the optical properties are governed by the interligand charge transfer (ILCT) among the three ligands. The formation of heteroleptic complexes induces the ILCT state even in nonpolar environments, thereby accelerating nonradiative decay and intersystem crossing. These findings mark significant advancements in photofunctional materials based on multinuclear complexes.

Conflicting Aromaticity in Trirhodium(I) Rosarin.

Aromaticity is one of the most important and widely used concepts in chemistry. Among the various experimentally discovered and theoretically predicted compounds that possess different types of aromaticity, conflicting aromaticity, where aromatic and antiaromatic electron delocalization is present in one molecule simultaneously, remains one of the most controversial and elusive concepts, although theoretically predicted 15 years ago. In this work, we synthesized a novel conflicting aromatic trirhodium complex that contains a σ-aromatic metal fragment surrounded by the π-antiaromatic organic ligand and characterized it by nuclear magnetic resonance spectroscopy, high-resolution mass spectrometry, and X-ray single crystal structure analysis. Experimental characterization and quantum chemical calculations confirm the unique conflicting aromaticity of the synthesized trirhodium molecule. Thus, this novel conflicting aromatic molecule expands the family of aromatic compounds. This discovery will enable researchers to develop and understand the phenomena of conflicting aromaticity in chemistry.

Guest-Responsive Near-Infrared-Luminescent Metal-Organic Cage Organized by Porphyrin Dyes and Yb(III) Complexes.

Metal-organic cages (MOCs) with luminophores have significant advantages for the facile detection of specific molecules based on turn-on or turn-off luminescence changes induced by host-guest complexation. One important challenge is the development of turn-on-type near-infrared (NIR)-luminescent MOCs. In this study, we synthesized a novel MOC consisting of two porphyrin dyes linked by four Yb(III) complexes, which exhibit bimodal red and NIR fluorescence signals upon photoexcitation of the porphyrin π system. Single-crystal X-ray structural analysis and computational molecular modeling revealed that planar aromatic perfluorocarbons were intercalated into the MOC. The tight packing between the MOC and guests enhanced the NIR fluorescence of Yb(III) by suppressing energy transfer from the photoexcited porphyrin to oxygen molecules. Guest-responsive turn-on NIR fluorescence changes in an MOC were successfully demonstrated.