Single-crystal X-ray Diffraction Research Articles

Synthesis, structural characterization, and theoretical analysis of novel zinc(ii) schiff base complexes with halogen and hydrogen bonding interactions.

In this article, we present the synthesis and characterization of three zinc(ii) complexes, [ZnII(HL1)2] (1), [ZnII(HL2)2]·2H2O (2) and [ZnII(HL3)2] (3), with three tridentate Schiff base ligands, H2L1, H2L2, and H2L3. The structures of the complexes were confirmed by single-crystal X-ray diffraction analysis. DFT calculations were performed to gain insights into the self-assembly of the complexes in their solid-state structures. Complex 1 exhibits dual halogen-bonding interactions (Br⋯Br and Br⋯O) in its solid-state structure, which have been thoroughly investigated through molecular electrostatic potential (MEP) surface calculations, alongside QTAIM and NCIPlot analyses. Furthermore, complex 2 features a fascinating hydrogen-bonding network involving lattice water molecules, which serves to link the [ZnII(HL2)2] units into a one-dimensional supramolecular polymer. This network has been meticulously examined using QTAIM and NCIplot analyses, allowing for an estimation of the hydrogen bond strengths. The significance of H-bonds and CH⋯π interactions in complex 3 was investigated, as these interactions are crucial for the formation of infinite 1D chains in the solid state.

Synthesis, characterization, and crystal structure of hexa-kis-(1-methyl-1H-imidazole-κN 3)zinc(II) dinitrate.

The synthesis of the title compound, [Zn(C4H6N2)6](NO3)2, is described. This complex consists of a central zinc metal ion surrounded by six 1-methyl-imidazole ligands, charge balanced by two nitrate anions. The complex crystallizes in the space group P. In the crystal, the nitrate ions are situated within the cavities created by the [Zn(N-Melm)6]2+ cations, serving as counter-ions. The three oxygen atoms of the nitrate ion engage in weak C-H⋯O inter-actions. In addition to single-crystal X-ray diffraction analysis, the complex was characterized using elemental analysis, 1H NMR, 13C NMR, and FTIR spectroscopy.

Synthesis and Stabilization of Highly Reactive Haloacetylium Ions.

The reactions of selected haloacetyl fluorides with the strong Lewis acids AsF5 and SbF5 were investigated in the aprotic solvent SO2ClF. Depending on the stoichiometric ratio of AsF5 or SbF5 and the haloacetyl fluorides, either O-coordinated adducts or the respective haloacetylium ions were isolated as solids. The compounds were characterized by low-temperature vibrational spectroscopy and single-crystal X-ray diffraction. [CClH2CO][Sb2F11] and [CH2FCO][Sb2F11] crystallize in the monoclinic space group P21 with two formula units per unit cell. The reactivity of the haloacetyl fluorides under Lewis acidic conditions is discussed based on quantum chemical calculations of fluoride ion affinities on the BP/def2SVPP level of theory. The haloacetylium ions are stabilized in the solid-state phase by intermolecular C···F contacts and electron donation of the fluorine ligands of the anions as well as intramolecular hyperconjugation.

Polytypism of incommensurately modulated structures of crystalline bromine upon molecular dissociation under high pressure

Polytypism of incommensurately modulated structures was hitherto unobserved. Here, it was found in solid bromine and iodine upon molecular dissociation under pressure up to 112 GPa. Single-crystal synchrotron x-ray diffraction in laser-heated diamond anvil cells revealed a number of allotropes of bromine and iodine, including polytypes of Br-IIIγ (Fmmm(00γ)s00) with γ varying within 0.18 to 0.3, coexisting at a given pressure. This finding opens a research area in the field of solid-solid phase transitions, disordered states of solid matter, and high-pressure structural studies. Published by the American Physical Society 2024

Cuparene-type sesquiterpenes with neuroprotective activities from the edible mushroom Flammulina filiformis

Four new cuparene-type sesquiterpenes, flammuterpenols A − D (1–4), along with one known congener (5) were isolated from the solid culture of edible mushroom Flammulina filiformis. Their structures with a benzoxabicyclo[3.2.1]octane core were elucidated by integrated multiple spectroscopic techniques, electronic circular dichroism, and single crystal X-ray diffraction analysis. Biologically, compounds 1–5 were evaluated in vitro for their neuroprotective effects against 6-hydroxydopamine induced cell death in human neuroblastoma SH-SY5Y cells. All of them exhibited remarkable neuroprotective effects possessing the EC50 values ranging from 0.93 ± 0.02 to 10.28 ± 0.10 μM. These findings not only enrich the structural diversity of cuparene-type sesquiterpenes, but also provide potential candidates for the further development of the neuroprotective agents.

A 1,4-benzoquinone with counteracting inductive donor and acceptor substituents

Investigation of a published route to produce 3,5-di- tert-butylphenol, starting from commercial 3,5-di- tert-butylbenzoic acid via 3,5-di- tert-butylanlinium hydrogen sulfate, unexpectedly yielded 2,6-dintitro-3,5-di- tert-butylphenol. Attempts to increase the yield of the latter resulted, instead, in the previously unreported 2,6-dinitro-3,5-di- tert-butylcyclohexa-2,5-dien-1,4-dione. Single-crystal X-ray diffraction structures are reported for the anilinium salt, the nitrated phenol, and the quinone. Voltammetry of the quinone shows two chemically reversible reductions in anhydrous solution and the radical anion produced from the first reduction step has been characterized by electron paramagnetic resonance spectroscopy. This compound fits well to the middle range of electron-poor quinones, indicating that the inductive effects of the tert-butyl and nitro groups counteract each other. This conclusion is also supported by the infrared spectroscopic data where the ν(C=O) and ν(C=C) bands are of very similar energy to those of 2,3,5,6-tetrachloro-1,4-benzoquinone.

Towards Nickel-NHC Fluoro Complexes-Synthesis of Imidazolium Fluorides and Their Reactions with Nickelocene.

While hundreds of complexes of the general formula [Ni(η5-C5H5)(NHC)(X)] exist (NHC = a N-heterocyclic carbene, X = Cl, Br, I), none is yet known with X = F. We attempted to prepare such a species by reacting nickelocene with imidazolium fluorides. Three imidazolium fluorides (ImH)+ F- [Im = (N,N'-bis-(R)-imidazolium: 1a, IMe, R = Me; 1b, IMes, R = 2,4,6-trimethylphenyl; 1c, IPr, R = 2,6-diisopropylphenyl)] were prepared and characterized by spectroscopic methods. In addition, the salts 1b [(IMesH)+ F-] and 1c [(IPrH)+ F-] were subjected single-crystal X-ray diffraction experiments. The reactions of these imidazolium fluorides with nickelocene did not lead to [Ni(η5-C5H5)(NHC)(F)] species. Instead, the reaction of 1a [(IMeH)+ F-] and 1b [(IMesH)+ F-] with nickelocene led to the salt 2 [Ni(η5-C5H5)(IMe)2]+ F- and to the square planar complex 3atrans-[NiF2(IMes)2] respectively. Both complexes were characterized spectroscopically and by single crystal X-ray diffraction. All four X-ray diffraction studies reveal hydrogen bonding and hydrogen interactions with the F atom or anion, and in some cases with solvent molecules of crystallization, and these phenomena are all discussed. Complex 2, in particular, exhibited a wide range of interesting H-bonded interactions in the solid state. Complexes 2 and 3a were tested as catalysts for Suzuki-Miyaura coupling but were not promising: complex 2 was inactive, and while 3a did indeed catalyze the reaction, it gave widely diverging results owing to its instability in solution.

Theoretical and experimental investigation on newly synthesized pyrazolopyridine derivatives: Insight into the compound activity, NLO response, and molecular dynamics

Pyrazolopyridine derivatives exhibiting biological activity are widely present in drug molecules. The title compound, ethyl 3-amino-6-methyl-4-(thiophen-2-yl)-1H-pyrazolo[3,4-b]pyridine-5-carboxylate (II), was designed and synthesized and the structure characterized by spectroscopic techniques and confirmed by single-crystal X-ray diffraction. The pyrazolopyridine moiety is not quite planar and the thiophene and ester groups are rotated well out of the mean plane of the pyridine ring. N—H···N and C—H···O hydrogen bonds plus π-stacking interactions form thick layers of molecules parallel to (001). Based on structural activity relationship studies, II exhibits potent activity against fibroblast collagenase-1 complexed to a diphenyl-ether sulphone-based hydroxamic acid or Matrix Metalloproteinase (MMP-1). Theoretical simulations were performed to probe the reactivity and electronic properties of II where the quantum theory of atoms in molecules and NBO analysis was used to describe the bonding nature and charge transfer excitation. The optical and nonlinear characteristics of II are also evidenced by its hyperpolarizability response. The kinetic and thermodynamic stability of II was monitored through a computed ab-initio molecular dynamics study. In addition, a Hirshfeld surface analysis was performed to assess the intermolecular interactions. Efficient binding of II in the MMP-1 complex system has been achieved through classical molecular dynamics and molecular docking calculations. An ADMET analysis was also carried out to explore the potential future drug candidacy of II.

Allanite-(Sm), CaSm(Al2Fe2+)(Si2O7)(SiO4)O(OH), the third samarium mineral from Jordanów Śląski, Lower Silesia, Poland

Abstract Allanite-(Sm), the third samarium mineral to be discovered, was studied using electron microprobe analysis and single-crystal X-ray diffraction. It is isostructural with monoclinic epidote-supergroup minerals and belongs to the allanite group. The mineral was found in a granitic pegmatite in a serpentine quarry near Jordanów Śląski in Lower Silesia, SW Poland. It occurs as subhedral to anhedral crystals with sizes of up to ~150 μm accompanied by allanite-(Nd), allanite-(Y), clinozoisite, hingganite-(Y), and xenotime-(Y). Allanite-(Sm) is yellowish-brown and shows a white streak, a vitreous luster, and a Mohs hardness of ~6. It is brittle, with conchoidal fracture and imperfect cleavage. The calculated density is 3.842 g·cm-3, and the calculated mean refractive index is close to 1.737. The holotype crystal contains (in wt%) 33.08(11) SiO2, 0.08(3) TiO2, 21.15(9) Al2O3, 0.45(6) Sc2O3, 0.48 Fe2O3(calc.), 0.02(1) V2O3, 2.49(31) Y2O3, 0.18(4) La2O3, 0.95(9) Ce2O3, 0.34(6) Pr2O3, 3.52(31) Nd2O3, 6.12(23) Sm2O3, 0.06(2) EuO, 3.25(21) Gd2O3, 0.34(2) Tb2O3, 0.94(7) Dy2O3, 0.15(4) Ho2O3, 0.16(3) Er2O3, 0.07(6) Tm2O3, 0.06(4) Yb2O3, 0.28(4) MnO, 8.38 FeO(calc.), 0.13(2) MgO, 13.71(15) CaO, and 1.95 H2O(+)calc.; the total is 98.04. The empirical EPMA + SREF formula is A1(Ca0.966Mn0.022Fe2+0.010)Σ0.998A2(Ca0.372Sm0.192Y0.121Nd0.114Gd0.098Ce0.032Dy0.028Pr0.011Tb0.010La0.006Er0.005Ho0.004Eu0.002Tm0.002Yb0.002)Σ0.998M1Al0.998M2Al0.998M3(Fe2+0.628Al0.275Sc0.036Fe3+0.033Mg0.018T i0.005V3+0.002)Σ0.998(T1–T3Si3.012O11)O(OH), the simplified formula is Ca(Sm,REE,Ca)Al2(Fe2+,Al,Fe3+)(Si2O7)(SiO4)O(OH), and the ideal formula is CaSm(Al2Fe2+)(Si2O7)(SiO4)O(OH), which requires (in wt.%) SiO2—30.37, Al2O3—17.18, Sm2O3—29.38, FeO—12.11, CaO—9.45, and H2O—1.52; the total is 100. Allanite-(Sm) is monoclinic, space-group P21/m, with the following unit-cell parameters: a = 8.8923(6), b = 5.7005(3), c = 10.1280(8) Å, β = 115.445(9)º, V = 463.59(6) Å3, Z = 2, and a : b : c = 1.5599 : 1 : 1.7767. The T site is exclusively occupied by Si, the A1 site is occupied by Ca and Mn, and the A2 site is mainly occupied by rare earth elements (REE), of which Sm is dominant. The M1 and M2 sites are occupied by Al and the M3 site by divalent cations, of which Fe2+, characteristic of allanite-type species, is dominant. Allanite-(Sm) and the associated allanite-(Y), allanite-(Nd), and hingganite-(Y) are secondary minerals precipitated from Ca-rich hydrothermal fluid during the metasomatic alteration of the Jordanów Śląski pegmatite. They accumulated REE released by the alteration of nearby xenotime-(Y). The disequilibrium rapid crystallization of REE-selective allanite and hingganite structures in an environment strongly enriched in heavy REE (HREE) relative to light REE (LREE), as well as small-scale heterogeneities in REE abundances in the fluid, resulted in the crystallization of exotic allanite species, including allanite-(Sm).

Synthesis of Silver(I) Complexes through In Situ Reactions of dppeda with dmp in the Presence of Silver Halides for Photocatalysis.

Due to the unique photosensitivity of silver compounds, they exhibit good photocatalytic activity as photocatalysts in the degradation of water pollutants. However, silver compounds have poor cycling stability and are prone to decomposition and reaction under light to form metallic silver, which greatly limits their practical application. Herein, a (2-(2-(diphenylphosphaneyl)ethyl)-9-methyl-1.10-phenanthroline (PSNNP)) pincer ligand was designed for stabilizing the central metal. The in situ-formed PSNNP ligand could be readily generated in one pot with the participation of silver halides. The reaction of silver halides with dppeda (N,N,N',N'-tetra(diphenylphosphanylmethyl)ethylene diamine) in the presence of dmp (2,9-dimethyl-1,10-phenanthroline) in acetonitrile afforded complexes Ag2X2 (PSNNP)2 (complexes 1, 2) (X = Cl, Br). Single-crystal X-ray diffraction shows that the tridentate coordination of the pincer ligand provides strong binding with metal centers and leads to high stability of the pincer metal unit. The removal rate of rhodamine B (RhB) by complexes 1 and 2 can reach up to 100%, demonstrating an excellent photocatalytic degradation performance for organic dyes. The important effect of PSNNP ligands on photocatalytic properties after coordination with central metals was studied through experiments and discrete Fourier transform (DFT) calculations. The photocatalytic reaction mechanism of complexes 1 and 2 was also studied. This result provides an effective pathway for the first synthesis of PSNNP and interesting insights into photocatalytic degradation chemistry.

Use of a confocal optical device for centring a diamond anvil cell in single-crystal X-ray diffraction experiments.

High-pressure crystallographic data can be measured using a diamond anvil cell (DAC), which allows the sample to be viewed only along a cell vector which runs perpendicular to the diamond anvils. Although centring a sample perpendicular to this direction is straightforward, methods for centring along this direction often rely on sample focusing, measurements of the direct beam or short data collections followed by refinement of the crystal offsets. These methods may be inaccurate, difficult to apply or slow. Described here is a method based on precise measurement of the offset in this direction using a confocal optical device, whereby the cell centre is located at the mid-point of two measurements of the distance between a light source and the external faces of the diamond anvils viewed along the forward and reverse directions of the cell vector. It is shown that the method enables a DAC to be centred to within a few micrometres reproducibly and quickly.

Switchable Photoelectric Response in High-Temperature Leadless Molecular Ferroelectric [C4N2H14][BiI5

Lead-free molecular ferroelectrics have garnered considerable attention for their promising potential, but such species with narrow band gap and sensitive photoelectric response are yet inadequate. Herein, we demonstrated the bulk ferroelectric photovoltaic effect in a novel lead-free molecular ferroelectric [C4N2H14][BiI5] with a Curie temperature (Tc) of 366 K and a narrow band gap (Eg) of 1.92 eV. The transformation of the crystal structure from the polar space group P21 to the nonpolar space group P21/m was elucidated using single-crystal X-ray diffraction. Room-temperature (RT) hysteresis loop reveals the intrinsic ferroelectricity of [C4N2H14][BiI5] with a relative small coercive field (Ec ∼ 0.27 kV/cm), saturation polarization (Ps ∼ 1.87 μC/cm2), and remanent polarization (Pr ∼ 1.61 μC/cm2). [C4N2H14][BiI5]-based solar device exhibits significant PV effects with a steady-state photocurrent (Jsc) of 3.54 μA/cm2 and a photovoltage (Voc) of 0.34 V under AM 1.5 G illumination, which can be significantly improved by adjusting the ferroelectric polarization, reaching a maximum Jsc of 140 μA/cm2 and Voc of 0.51 V. This work offers a promising avenue for lead-free molecular ferroelectric materials in the field of optoelectronic devices.

Seven New Noroleanane Triterpenoids from Mastic and their NO Inhibitory and Cytotoxic Activities.

Mastic is a natural resin produced by Pistacia lentiscus L. (Anacardiaceae) with high medicinal value and have been traditionally used as Uighur imported medicine for centuries. In this study, 16 triterpenoids including seven new norleananetriterpenoids (1-7), along with nine known oleanane triterpenoids (8-16), were isolated from the mastic. Their chemical structures were determined on the basis of extensive spectroscopic analyses (including IR, UV, ESI-HR-MS and NMR spectroscopy) and single-crystal X-ray diffraction. Compounds 4-7, 11, 14 and 16 showed strong inhibitory NO productionin LPS-induced RAW264.7 cells with IC50 values 7.44-9.76 μM, respectively (positive control dexamethasone, 9.93 ± 1.17 μM). Furthermore,compounds 3 and 12 significantly inhibited the growth of SW480 cells, compound 3 showed the most pronounced inhibitory effect with an IC50 of 2.30 ± 0.38 μM.

Highly Efficient Detection of Pd2+ in Aqueous Medium by an Elusive Mn(II) Coordination Polymer

Herein, we report the synthesis of a Mn(II)‐based coordination polymer (CP); and its structure, phase consistency and thermal stability have been established by single‐crystal X‐ray diffraction (SCXRD), powder X‐ray diffraction (PXRD) and thermalgravimetric analysis (TGA) respectively. This is the first example of paramgnetic Mn(II)‐based CP that acts as pH‐dependent emitting material [lem= 525 nm (pH = 2.0‐4.0) and 450 nm (pH = 5.0‐12.0)]. Its emission is quenched by Pd2+ in aqueous medium in presence of other thirteen cations with reasonably low pH‐dependent limits of detection (LODs) [21.178 ppb (pH= 3), 15.005 ppb (pH = 7.0) and 59.940 ppb (pH = 10.0)] as described by well‐established mechanism. Therefore, urgency of such stable sensor remains high in regard to the environmental pollution.

Silver(I) complexes with antifungal drug econazole: Structural characterization and antimicrobial activity study

Two new silver(I) complexes with the antifungal agent econazole (ecz) of the general formula [Ag(еcz)2]X, X = CF3SO3− (Ag1) and PF6− (Ag2), were synthesized and structurally characterized by spectroscopic (1H NMR, IR and UV–Vis) and electrochemical methods. The crystal structure of Ag2 was determined by single crystal X-ray diffraction analysis, confirming an ideal linear geometry of the silver(I) ion in this complex. In addition, by utilising Hirshfeld surface analysis (HSA), it was verified that the crystal structure of Ag2 is stabilized by H⋯H, H⋯Cl, C⋯H, and H⋯F interactions. Density functional theory (DFT) calculations provided additional evidence for formation of the complexes in the solid state and their stability in solution. The coordination of ecz to the silver(I) ion endowed this agent with antibacterial activity against Gram-positive (Pseudomonas aeruginosa and Escherichia coli) and Gram-negative (Staphylococcus aureus and Listeria monocytogenes) bacteria. The most significant antibacterial activity of Ag1 and Ag2 was observed against S. aureus with 56- and 73-fold improvement, respectively, compared to the parent drug. Moreover, a study of the bacterial antibiofilm activity revealed that these complexes were able to prevent approximately 90 % of biofilm formation at their low concentrations. Also, both complexes have shown more pronounced anti-Candida activity than econazole itself, being less toxic on the human normal fibroblast cell line MRC-5. The total amount of ergosterol was reduced in the presence of the subinhibitory concentrations of Ag1 and Ag2 complexes, which was also confirmed by a molecular docking study with two isomers of cytochrome P450 sterol 14α-demethylase, CYP51B and CYP130, as target receptors.

Temperature dependent self-assembly of lanthanide coordination polymers based on a benzimidazolium dicarboxylate linker: synthesis, structure and luminescence properties

Five new coordination polymers, namely [Ln(L)(NO3)2]n (Ln = La (1), Pr (2) and Sm (3)), [Eu(L)(NO3)2·1.5H2O]n (4) and [Tb(L)(OAc)2(H2O)·3H2O]n (5) (HOAc = CH3COOH), were synthesised by reaction of lanthanide nitrates with 1,3-bis(4-carboxybenzyl)benzimidazolium chloride (H2L+Cl−) under solvothermal conditions. All the coordination polymers were characterised by powder X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, elemental analysis and single crystal X-ray diffraction. Complexes 1–5 exhibit two different 2-D structures due to the variation in reaction temperature. Complexes 1–4 are isostructural and crystallised in the monoclinic system, C2/c space group, showing a two-dimensional layer with Ln chains linked by L− ligands. Complex 5 crystallised in the P21/n space group, featuring a 2-D layer different from 1–4 with Tb dimers linked by L− ligands through carboxylates. Further, the luminescence properties of complexes 3–5 were investigated. In addition, the fluorescence lifetime and quantum efficiency of complex 4 were measured.

Polynitro-1,2,4-triazole Energetic Materials with N-Amino Functionalization.

Trinitromethyl and N-amino groups were innovatively incorporated into the framework of 1,2,4-triazole, resulting in 1-amino-5-nitro-3-(trinitromethyl)-1,2,4-triazole (2). Ammonium and hydrazinium salts of 1-amino-5-nitro-3-(dinitromethyl)-1,2,4-triazole were synthesized by acidification, extraction, and neutralization with bases from the potassium salt. All of the newly prepared energetic compounds were comprehensively characterized by using infrared spectroscopy, elemental analysis, nuclear magnetic resonance spectroscopy, and single crystal X-ray diffraction. Compound 2 exhibits favorable properties such as positive oxygen balance (OBCO2 = 5.8%), high density (1.88 g cm-1), good detonation performances (vD = 8937 m s-1, P = 35.5 GPa), and appropriate friction sensitivity (FS = 144 N). The potassium salt 3 demonstrates good thermal decomposition temperature (181 °C) and high density (1.98 g cm-1), while the ammonium salt and hydrazinium salt also display good thermal decomposition temperatures of 183 and 176 °C, respectively. Among these compounds, the ammonium salt exhibits the lowest mechanical sensitivities (FS = 144 N, IS = 6 J).

A Self-Healing Crystal That Repairs Multiple Cracks.

We report both cracking and self-healing in crystals occurring during a thermal phase transition, followed by a topochemical polymerization. A squaramide-based monomer was designed where the azide and alkyne units of adjacent molecules are positioned favorably for a topochemical click reaction. The monomer undergoes spontaneous single-crystal-to-single-crystal (SCSC) polymerization at room temperature via regiospecific 1,3-dipolar cycloaddition, yielding the corresponding triazole-linked polymer in a few days. When heated at 60 °C, the polymerization completes in a SCSC manner in 24 h. Upon continuous heating from room temperature to 110 °C, the monomer crystals develop multiple cracks, and they self-heal immediately. The cracking occurs due to a thermal phase transition, as evidenced by differential scanning calorimetry (DSC). The cracks heal either upon further heating or upon cooling of the crystals due to the topochemical polymerization or reversal of the phase transition, respectively. Increasing the heating rate leads to the formation of longer and wider cracks, which also heal instantaneously. The self-healed crystals retained their integrity and the crystal structure of the self-healed crystals was analyzed by single-crystal X-ray diffraction. The quality of the self-healed crystals and their diffraction ability conform to those of the completely reacted crystals at room temperature or at 60 °C without developing cracks. This work demonstrates a novel mechanism for self-healing of molecular crystals that could expand the horizon of these materials for a plethora of applications.

Synthesis, Structural, Electrochemical, and DFT Studies of Highly Substituted Nonplanar Ni(II) Porphyrins and Their Intensity-Dependent Third-Order Nonlinear Optical Properties.

We designed and successfully synthesized highly substituted electron-deficient nonplanar Ni(II) porphyrins and their derivatives (1-7) in moderate to good yields. These derivatives were comprehensively characterized by various spectroscopic techniques and single-crystal X-ray diffraction (SCXRD) analysis. SCXRD analysis confirmed the structures of compounds 2, 4, and 7, adopting saddle-shape geometry. These nonplanar porphyrins demonstrated significant bathochromic shifts in their absorption spectra compared to parent NiTPP, attributed to the influence of bulky β-substituents and/or peripheral fusion. π-Extended porphyrins 6 and 7 displayed panchromatic absorption spectra extending into the NIR region. Porphyrins 6 and 7 demonstrated a profound anodic shift (∼400 mV) in their first reduction peak potentials compared to precursor NiTPP(NO2)Br6. The experimental absorption spectral pattern matches the simulated absorption spectra obtained from TD-DFT studies. The femtosecond laser intensity-dependent third-order nonlinear optical studies revealed that NiDFP(VCN)2Br6 (6) and NiDFP(VCN)2(PE)6 (7) displayed giant optical nonlinearities compared to the other porphyrins. Among all, NiDFP(VCN)2Br6 (6) possessed the highest two-photon absorption coefficient (β) and cross-section (σTPA) values in the range of 22-33 × 10-10 m/W and 3.77-6.95 × 106 GM, respectively. These findings suggest that the investigated nonplanar π-extended porphyrins are promising candidates for future optoelectronic applications.

Structural Isomerism in Bimetallic Ag20Cu12 Nanoclusters.

Structural isomers of atomically precise metal nanoclusters are highly sought after for investigating structure-property relationships in nanostructured materials. However, they are extremely rare, particularly those of alloys, primarily due to the challenges in their synthesis and structural characterization. Herein, for the first time, a pair of bimetallic isomeric AgCu nanoclusters has been controllably synthesized and structurally characterized. These two isomers share an identical molecular formula, Ag20Cu12(C≡CR)24 (denoted as Ag20Cu12-1 and Ag20Cu12-2; HC≡CR is 3,5-bis(trifluoromethyl)phenylacetylene). Single-crystal X-ray diffraction data analysis revealed that Ag20Cu12-1 possesses an Ag17Cu4 core composed of two interpenetrating hollow Ag11Cu2 structures. This core is stabilized by four different types of surface motifs: eight -C≡CR, one Cu(C≡CR)2, one Ag3Cu3(C≡CR)6, and two Cu2(C≡CR)4 units. Ag20Cu12-2 features a bitetrahedron Ag14 core, which is stabilized by three Ag2Cu4(C≡CR)8 units. Interestingly, Ag20Cu12-2 undergoes spontaneous transformation to Ag20Cu12-1 in the solution-state. Density functional theory calculations explain the electronic and optical properties and confirm the higher relative stability of Ag20Cu12-1 compared to Ag20Cu12-2. The controlled synthesis and structural isomerism of alloy nanoclusters presented in this work will stimulate and broaden research on nanoscale isomerism.