Experimental Electronic Spectra Research Articles

Identification of cholesterol in different media by using the FT-IR, FT-Raman and UV–visible spectra combined with DFT calculations

In this investigation, the experimental FT-IR and FT-Raman spectra of cholesterol in the solid phase and in ethanol solution have been combined with the B3LYP/6–311++G** calculations and the scaled quantum mechanical force field (SQMFF) methodology, normal internal coordinates and transferable scaling factors to obtain the complete vibrational assignments of 216 vibration modes expected. Hence, complete vibrational assignments for that steroid of greatest biological importance are reported for first time in gas phase and ethanol solution together with its scaled force constants. Changes in the positions of some bands and in force constants values are observed in the different media due to the predicted intra-molecular interactions between CH3/CH3, CH3/CH2 and CH2/CH2 groups by atoms in molecules (AIM) calculations. The 1H- and 13C NMR chemical shifts of normal and deuterated cholesterol in aqueous solution confirm that the H atom of OH group is involved in the formation of H bonds in solution. Studies of experimental electronic spectra of cholesterol in different concentrations of ethanol revealed that the positions of peaks maxima increase conform increase the solution concentration. The natural bond orbital (NBO) analyses reveal that the polar OH group and the four fused rings play important roles in the stability and properties of cholesterol than the large hydrophobic moiety. Frontier orbitals predicted low reactivity of cholesterol in ethanol probably due to its high ω value in this medium.

Bioassay-Guided Isolation and Identification of Cytotoxic Compounds from Melaleuca quinquenervia Fruits.

The fruit extract of Melaleuca quinquenervia yielded a total of 19 compounds, including two novel spiro-biflavonoid enantiomers (1a and 1b) and a chalcone derivative (3). Their structures were determined through spectroscopic analysis. The enantiomers of the racemic mixture of compound 1 were successfully resolved into (+)-1 and (-)-1 using chiral-phase HPLC. Single-crystal X-ray diffraction analysis was also used to confirm the structure of 1. The enantiomeric configurations of 1 and 2 were determined through a comparison of the calculated and experimental electronic circular dichroism spectra. Compounds 2 (melanervin), 14 (methyl betulinate), 15 (3-O-acetylbetulinic acid), and 16 (pyracrenic acid) were found to be highly cytotoxic, with compound 16 showing superior growth inhibition of nonsmall cell lung cancer cells (A549 cells) (IC50 2.8 ± 0.1 μM) compared to cisplatin (IC50 3.3 ± 0.0 μM), a positive control chemotherapeutic drug. Both compound 16 and cisplatin were significantly more cytotoxic toward A549 lung cancer cells compared to nontumorigenic Vero E6 cells.

Hyphenation of lipophilic ruthenium(II)-diphosphine core with 5-fluorouracil: an effective metallodrug against glioblastoma brain cancer cells.

Glioblastoma multiforme (GBM) is the most common highly aggressive malignant brain tumor, with a very limited chance for survival post-diagnosis and post-treatment. Despite significant advancement in GBM genomics implicated in molecularly targeted chemotherapies, the prognosis remains poor and requires new drug discovery approaches. We used fluoropyrimidine 5-fluorouracil (5-FU), an antimetabolite anticancer drug conjugated or 'caged' within a lipophilic Ru(II)-diphosphine (dppe) core formulated as [RuII(dppe)2(5-FU)]PF6 (Ru-DPPE-5FU), where dppe = 1,2-bis(diphenylphosphino)ethane, and evaluated its in vitro cytotoxicity in depth with aggressive GBM cells (LN229). The hydrophilic nature of 5-FU limits its passage through the blood-brain barrier (BBB), which prevents its effective accumulation and efficacy for GBM tumors. Herein, we attempted to modulate the lipophilicity of 5-FU by inserting it within a well-designed lipophilic {Ru(dppe)2}-core with anticipated higher efficiency towards GBM. The physicochemical properties of [RuII(dppe)2(5-FU)]PF6 (Ru-DPPE-5FU) were studied using various spectroscopic and analytical techniques. The molecular structure was determined using X-ray crystallography, showing a distorted {RuP4NO} octahedral geometry with bidentate (N, O) binding of 5-FU and its aromatization in the Ru(II)-bound form. The 31P-NMR spectra of Ru-DPPE-5FU showed four closely spaced distinct 31P-signals, indicating four unique chemical environments around P, and the strong coupling constants between them make it a second-order spectrum. The RuII/RuIII redox potential in Ru-DPPE-5FU shifted by ∼0.91 V towards the anodic region as compared to its precursor complex cis-[Ru(dppe)2Cl2] (Ru-DPPE-Cl). DFT-based theoretical calculations have been performed to correlate the experimental electronic absorption spectra and redox behaviours of the complexes. The electrostatic potential (ESP) plots indicate the delocalization of the charge density on the O-/F-atom from the 5-FU ligand towards Ru(II) upon its complexation. The antioxidant properties of all the compounds were quantified by a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. The hyphenation of the 5-fluorouracil (5-FU) ligand to the lipophilic {Ru(dppe)2}-core endowed lipophilicity to Ru-DPPE-5FU with higher in vitro cytotoxicity (IC50 = 2.37 μM) against the LN229 GBM cells as compared to the hydrophilic 5-FU, suggesting efficient cellular uptake. Further biological assays indicated that the complex is highly potent in inhibiting significant proliferation and spheroid formation and restricting the migratory potentials of the GBM cells. Increased caspase 3/7 activity and the presence of apoptotic bodies at the center of 3-D GBM spheroids as revealed by AO/EB dual staining indicated a deeper penetration of the lipophilic complex. The Ru-DPPE-5FU complex displayed lower cytotoxicity in HaCaT normal cells (IC50 = 7.27 μM) in comparison to LN229 cancer cells with a selectivity index (S.I.) of ≥3. Overall, the synergism and caging of 5-FU within the hydrophobic {Ru(dppe)2}-core improves the pharmacokinetic profile of Ru-DPPE-5FU as a potent anticancer agent for glioblastoma.

Fluorescent turn on detection of zinc(II) ion using a hydrazone derived from 4-tert-butyl-2,6-diformylphenol and 3-hydrazineylquinoxalin-2(1H)-one

A polydentate chelating ligand (LH) was synthesized from 4-tertbutyl-2,6-diformylphenol and 3-hydrazineylquinoxalin-2(1H)-one and characterized by mass spectrometry, IR and NMR spectroscopy. LH is weakly fluorescent in EtOH – HEPES buffer (5 mM, pH = 7.4, 8:2, v/v) but exhibited a turn on response with Zn2+ ion having a workable pH range of 6–12 and thus is compatible with biological pH. This sensor is selective for Zn2+ ion, over various metal ions and anions as evident from competition experiments. The probable mechanism of sensing by LH is restriction of ESIPT, PET and C = N isomerization processes and on-set of CHEF process upon coordination to Zn(II) ion. Reversibility was established using EDTA test and applicability in various real samples were evaluated. The calculated limit of detection for Zn2+ ion was 95 nM and Job plot as well as 1H NMR titration suggested a 2:1 binding ratio between Zn2+ ion and LH. From the reaction (in ethanol) of ZnCl2 with LH, in 2:1 ratio, crystalline solids of composition [Zn2(L)Cl3]⋅2H2O 2.5DMF was isolated and its molecular structure was established by single crystal XRD studies. DFT/TDDFT calculation supported the experimental electronic absorption spectrum.

Isolated Dimers Versus Solid-State Dimers of N-Heteropolycycles: Matrix-Isolation Spectroscopy in Concert with Quantum Chemistry.

In this work, matrix-isolation spectroscopy and quantum-chemical calculations are used together to analyse the structure and properties of weakly bound dimers of the two isomers benzo[a]acridine and benzo[c]acridine. Our measured experimental electronic absorbance spectra agree with simulated spectra calculated for the equilibrium structures of the dimers in gas-phase, but in contrast, disagree with the simulated spectra calculated for the structures obtained by optimising the experimental solid-state structures. This highlights the sensitivity of the electronic excitations with respect to the dimer structures. The comparison between the solid-state and gas-phase dimers shows how far the intermolecular interactions could change the geometric and electronic structure in a disordered bulk material or at device interfaces, imposing consequences for exciton and charge mobility and other material properties.

Computational optimal transport for molecular spectra: The fully continuous case.

Computational optimal transport is used to analyze the difference between pairs of continuous molecular spectra. It is demonstrated that transport distances which are derived from this approach may be a more appropriate measure of the difference between two continuous spectra than more familiar measures of distance under many common circumstances. Associated with the transport distances is the transport map which provides a detailed analysis of the difference between two molecular spectra and is a key component of our study of quantitative differences between two continuous spectra. The use of optimal transport for comparing molecular spectra is developed in detail here with a set of model spectra, so that the discussion is self-contained. The difference between the transport distance and more common definitions of distance is elucidated for some well-chosen examples and it is shown where transport distances may be very useful alternatives to standard definitions of distance. The transport distance between a theoretical and experimental electronic absorption spectrum for SO2 is studied and it is shown how the theoretical spectrum can be modified to fit the experimental spectrum better adjusting the theoretical band origin and the resolution of the theoretical spectrum. This analysis includes the calculation of transport maps between the theoretical and experimental spectra suggesting future applications of the methodology.

Five-coordinated bis-dioxolene cobalt complexes with triphenylphosphine

Three novel five-coordinated bis-dioxolene cobalt complexes with triphenylphosphine were synthesized. Complexes differ by dioxolene ligands: 3,6-di-tert-butylcyclohexa-3,5-diene-1,2-dione (complex 1), 5,8-di-tert-butyl-2,3-dihydro-1,4-ethanoquinoxaline-6,7-dione (complex 2), 3,6-di-tert-butyl-4-methoxycyclohexa-3,5-diene-1,2-dione (complex 3). The geometry of the inner coordination core of all compounds is close to square pyramidal. The base of the pyramid is formed by oxygen atoms of the dioxolene ligands whereas phosphine occupies the apical position. The planes of dioxolenes are slightly bent relative to each other. The magnetic moment values at low temperatures correspond to one unpaired electron per molecule for all complexes. In the complex containing a methoxy group in the dioxolene ligand (3), an increase in the magnetic moment is observed upon heating above 250 K, which indicates the appearance of a fraction of molecules with a higher spin multiplicity. A slight elongation of the Co-O, Co-P distances and shortening of the CO bonds is observed at 353 K. DFT calculations using the TPSSh functional correctly reproduce geometries of the complexes as well as their electronic absorption and vibrational spectra. DFT predicts the doublet-state complexes to possess the lowest enthalpies. Gibbs free energy of sextet complex 3 in solution is lower than that of its doublet state. This agrees well with the experimental electronic absorption spectra. On the basis of TD DFT calculations, a strong NIR absorption band in the spectra of low-spin 1 and 2 is assigned to the transition involving charge transfer from cobalt to the dioxolene and PPh3 ligands (MLCT). The doublet molecules can be described by the (↑SQ—)(Co3+)(Cat2—) ↔ (Cat2—)(Co3+)(↑SQ—) resonance structures. The sextet state in all three systems represents the (↑SQ—)(↑↑↑Co2+)(PPh3)(↑SQ—) bis-semiquinonate complex of high-spin Co(II). On the basis of the conventional description the doublet → sextet transition in complexes can be interpreted as a VT/SCO transformation. The electron density analysis of the doublet → sextet transition in the 1 and 3 molecules reveals areas of both increase and decrease in the charge density near the Co and O atoms.

Sulfur-Containing Radical Anions Formed by Photolysis of Thiosulfate: Quantum-Chemical Analysis.

The photochemistry of sodium thiosulfate (S2O32-) in aqueous solutions is rather complicated. Several sulfur-containing radical anions are formed upon photoexcitation. Any of them are rather common (SO3•-, SO2•-, and SO5•-); others are rare (S2O3•-, •S4O63-, and S•-) or never documented (S2O5•-). In order to support the identification of intermediate radical anions, quantum-chemical (QM─quantum mechanical) calculations of the geometric and electronic structures of S2O3•-, S2O5•-, and •S4O63- were performed. Two different approaches, time-dependent density functional theory and complete active space self-consistent field, were applied to identify the method optimal for the reproduction of the experimental electronic absorption spectra. Several of the most commonly used functionals were considered. The best agreement with the experimentally observed spectra of reference compounds (common sulfur-containing anions and radical anions) was achieved for the WB97X-D3 functional. Using this approach, satisfactory agreement between experimental and calculated spectra of S2O3•-, S2O5•-, and •S4O63- was achieved. It was shown that S2O5•- and •S4O63- can exist in two isomeric forms with different spectral properties. These isomers are S2O3O2•-; SO3SO2•- for the case of S2O5•- and (S2O3)2•3-; (S3O32-...SO3•-) for the case of •S4O63-.

Synthesis, molecular structure, mesomorphism and DFT/TD-DFT calculations of square-planar bis[1-((p-tolylimino)methyl)naphthalen-2-olato-κ2N,O]nickel and copper(II) complexes

Reaction of the Schiff base ligand (E)-1-((p-tolylimino)methyl)naphthalen-2-ol (HL) with nickel(II) and copper(II) acetate provides the bis[1-((p-tolylimino)methyl)naphthalen-2-olato-κ2N,O]Ni and Cu(II) complexes (1 and 2), respectively. X-ray structure determinations reveal coordination of two N,O-chelate Schiff base ligands to the metal ion in a square-planar geometry for both the complexes. The phase purity of bulk microcrystalline samples is confirmed by Powder XRD patterns. The solid-state magnetic moment (µeff = 2.73 (1) and 2.06 µB (2)) indicates paramagnetic nature of the complexes. Thermal analyses by differential scanning calorimetry (DSC) and polarizing light microscopic (PLM) observations suggest mesomorphic property for 2. Cyclic voltammograms recommend a quasi-reversible two one electron charge transfer processes for 2 in dimethylformamide. Geometry optimization and excited state properties by DFT/TD-DFT calculations reproduce the experimental bond distances and angles as well as the experimental electronic spectra.

A five-carbon unsaturated Criegee intermediate: synthesis, spectroscopic identification, and theoretical study of 3-penten-2-one oxide.

Biogenic alkenes, such as isoprene and α-pinene, are the predominant source of volatile organic compounds (VOCs) emitted into the atmosphere. Atmospheric processing of alkenes via reaction with ozone leads to formation of zwitterionic reactive intermediates with a carbonyl oxide functional group, known as Criegee intermediates (CIs). CIs are known to exhibit a strong absorption (π* ← π) in the near ultraviolet and visible (UV-vis) region due to the carbonyl oxide moiety. This study focuses on the laboratory identification of a five-carbon CI with an unsaturated substituent, 3-penten-2-one oxide, which can be produced upon atmospheric ozonolysis of substituted isoprenes. 3-Penten-2-one oxide is generated in the laboratory by photolysis of a newly synthesized precursor, (Z)-2,4-diiodopent-2-ene, in the presence of oxygen. The electronic spectrum of 3-penten-2-one oxide was recorded by UV-vis induced depletion of the VUV photoionization signal on the parent m/z 100 mass channel using a time-of-flight mass spectrometer. The resultant electronic spectrum is broad and unstructured with peak absorption at ca. 375 nm. To complement the experimental findings, electronic structure calculations are performed at the CASPT2(12,10)/aug-cc-pVDZ level of theory. The experimental spectrum shows good agreement with the calculated electronic spectrum and vertical excitation energy obtained for the lowest energy conformer of 3-penten-2-one oxide. In addition, OH radical products resulting from unimolecular decay of energized 3-penten-2-oxide CIs are detected by UV laser-induced fluorescence. Finally, the experimental electronic spectrum is compared with that of a four-carbon, isoprene-derived CI, methyl vinyl ketone oxide, to understand the effects of an additional methyl group on the associated electronic properties.

A new strategy for the synthesis of oxo-rhenium(V) porphyrins: Synthesis, characterization, theoretical calculations and electrochemical aspects

A new synthesis procedure has been developed for the preparation of oxo-rhenium(V) porphyrins using melted benzoic acid. Here we have demonstrated this method using three representative compounds namely O=ReV(TPP)(OOCPh) (1), O=ReV(TMP)(OOCPh) (2), and O=ReV(TCP)(OOCPh) (3) [where TPP = 5,10,15,20-meso-tetraphenylporphyrin, TMP = 5, 10, 15, 20-meso-tetra(p-methoxy)phenylporphyrin and TCP = 5, 10, 15, 20-meso-tetra(p-chloro)phenylporphyrin]. The yield percentage is higher than any other method reported earlier. All the compounds were well characterized by C, H and N microanalysis, ESI-MS, IR, UV–vis and 1H NMR spectroscopic techniques. On treating with mild bases like pyridine, imidazole, dil. NH4OH compound 1 instantly gets converted to µ-oxo bridged dimeric oxorhenium(V) complex µ-O-[ReO(TPP)]2 (4). The electrochemical behavior of the synthesized compounds has been examined by the cyclic voltammetric method. Theoretical calculations like geometry optimization, electronic energy, frequency, and frontier molecular orbital (FMO) energy level diagram for compound 1 have been investigated by Density Functional Theory (DFT) method. The experimentally calculated HOMO-LUMO energy gap and the experimental electronic spectrum were found to agree well with the value obtained from DFT studies.

Conformational and solvent effects in structural and spectroscopic properties of 2-hydroxyethyl methacrylate and acrylic acid

• 2-Hydroxyethyl methacrylate (HEMA) and acrylic acid (AA) were investigated through MD simulations and DFT calculations. • Properties derived from simulations were compared to experimental electronic and vibrational spectra. • Different solvation models were used in theoretical spectra calculation. 2-hydroxyethyl methacrylate (HEMA) and acrylic acid (AA) are monomers widely used in the production of hydrogels with medium-high water content. The structural and spectroscopic properties of HEMA and AA were studied using a combination of computational strategies based on both density functional theory (DFT) calculations and molecular dynamics (MD) simulations. DFT calculations have confirmed the co-existence of two stable HEMA conformers, while solute-solvent interactions between HEMA and AA with water were characterized by the analysis of MD simulations carried out by employing four different water models and different simulation conditions. The carbonyl and hydroxyl oxygen atoms of HEMA are involved in hydrogen bonding, whereas the ester oxygen atom does not appreciably interacts with the solvent. No significant differences in solute-solvent interactions are found between the two HEMA conformers. Their spectroscopic properties were calculated and the results were compared to experimental data. Although electronic spectra do not really allow a differentiation of the conformers, IR spectra present some peculiar bands to discriminate the presence and obtain information on the ratio of the conformers in solution. To verify the influence of a solvent with higher dipole moment on chemical properties, acetonitrile has been considered as an alternative solvent.

Structural, spectroscopic and computational studies of two new spirocompounds containing 2,3,4-trimethoxybenzyl group

Two new spirocompounds have been obtained by two different routes. Compound A1 was prepared in a solution of TEAF to connect the trimethoxybenzyl unit with the dioxaspirounit by a single bond. However, Compound A2 was prepared in ethanol to join the trimethoxybenzyl unit with the dioxaspirounit by a double bond. The result of X-ray single-crystal diffraction verifies the two compounds are both the monoclinic systems, space group P21/n (A1) and P21/c (A2). 1D-chained structure was formed by C(1)−H(1A)···O(4) intermolecular hydrogen bonds in A1. However, a 2D frame-work was obtained by C(8)−H(8C)···O(5) hydrogen bonds in A2. The DFT optimized geometric structures with the B3LYP/6–31 G (d, p) basis set are in accord with those crystallographic studies. The experimental and theoretical vibrational frequencies and electronic spectra of A1 and A2 have been investigated. In addition, MEP, NBO and thermodynamic properties have also been studied.

Synthesis, Crystal Structures, and Density Functional Theory Studies of Two Salt Cocrystals Containing Meldrum's Acid Group.

Two salt cocrystals, C31H34N4O8 (DDD) and C17H20N2O8 (MDD), were synthesized and their structures were determined by single-crystal X-ray diffraction. DDD is made up of one (C13H13O8)− anion, one (C9H11N2)+ cation, and one 5,6-dimethyl-1H-benzo[d]imidazole molecule. MDD consists of one (C4H7N2)+ cation and one (C13H13O8)− anion. DDD and MDD belong to the monoclinic, P21/c space group and triclinic, P-1 space group, respectively. A 1D-chained structure of DDD was constituted by N–H···N and N–H···O hydrogen bonds. However, a 1D-chained structure of MDD was bridged by N–H···O hydrogen bonds. Their density functional theory-optimized geometric structures with a B3LYP/6-311G(d,p) basis set fit well with those of crystallographic studies. By calculating their thermodynamic properties, the correlation equations of C0p,m, S0m, H0m, and temperature T were obtained. By comparing the experimental electronic spectra with the calculated electronic spectra, it is found that the PBEPBE/6-311G(d,p) method can simulate the UV–Vis spectra of DDD and MDD. In addition, the fluorescence spectra in the EtOH solution analysis show that the yellowish-green emission occurs at 570 nm (λex = 310 nm) for DDD and the purplish-blue emission occurs at 454 nm (λex = 316 nm) for MDD.

2,5-Bis(5-tert-butyl-benzoxazole-2-yl) thiophene (BTBB): spectroscopic behavior, dipole moment, laser behavior, DFT and TD-DFT investigations

In various solvents, the experimental electronic UV-Vis absorption and emission spectra of 2,5-Bis(5-tert-butyl-benzoxazole-2-yl) thiophene (BTBB) were assessed. For the BTBB geometrical structure, the dipole moment, laser activity, and experimental luminescence spectra have been investigated in different solvents. Furthermore, the photostability of the BTBB model structure exploitation utterly varied solvents like methanol, amyl alcohol, and dimethylformamide (DMF) in terms of approach for calculating half-life methodology (pumping with nitrogen laser 337.1 nm), yet because of the range of pulses needed to cut back the studied molecule intensity to 50% of its original value. The B3LYP/6-311G (d, p) level of theory was wont to optimize the BTBB geometrical structure. On the other hand, TD-M06-2X/6-311++(3d, 3p) is employed to get calculated spectral behaviors for the molecule under investigation. The computational electronic UV-Vis absorption spectra of the BTBB molecule in various solvents were computed exploitation time dependent density functional theory (TD-DFT) at the M06-2X/6-311++(3d, 3p) level. Theoretical findings were contrasted with experimental findings. The results reveal that the computational optical characteristics of the investigated molecular structure accord with the experimental findings.

Structural and electronic investigation of 3,4-dihydropyrimidin-2(1H)-ones (DHPMs): Correlations between spectroscopic and molecular docking features upon salmon sperm DNA

A set of 3,4-dihydropyrimidin-2(1H)-ones (DHPMs) was prepared via a “one-pot” three-component Biginelli reaction using different aldehydes, ethyl acetoacetate, urea, and catalyzed by iron chloride hexahydrate. Subsequently, these compounds were submitted to chemical oxidation with nitric acid in order to obtain their respective oxidized forms. Density functional theory (DFT) was applied to investigate the structural, electronic, and bonding characteristics of these compounds. This study results show that in the DHPMs (1-3), the six-membered ring adopts a pseudo-boat conformation, and the heights of the C4 and N1 atoms from the boat plane depend on the type of the substituent on the aryl ring. Experimental electronic spectra for all compounds were recorded and compared with simulations obtained by time-dependent-DFT (TD-DFT). The interaction between those DHPMs and salmon sperm DNA was monitored spectrophotometrically in the UV region, binding constants (Kb) were estimated, and docking studies were performed using the PatchDock® server. Considering the differences in overall planarity and spectral signature of the compounds studied, we concluded that the reduced DHPMs are prone to achieve partial intercalation of their structures between the DNA nitrogen base pairs while the oxidized ones prefer to stay deep inside of the minor groove of this biomolecule.

Computational optimal transport for molecular spectra: The semi-discrete case.

Comparing a discrete molecular spectrum to a continuous molecular spectrum in a quantitative manner is a challenging problem, for example, when attempting to fit a theoretical stick spectrum to a continuous spectrum. In this paper, the use of computational optimal transport is investigated for such a problem. In the optimal transport literature, the comparison of a discrete and a continuous spectrum is referred to as semi-discrete optimal transport and is a situation where a metric such as least-squares may be difficult to define except under special conditions. The merits of an optimal transport approach for this problem are investigated using the transport distance defined for the semi-discrete case. A tutorial on semi-discrete optimal transport for molecular spectra is included in this paper, and several well-chosen synthetic spectra are investigated to demonstrate the utility of computational optimal transport for the semi-discrete case. Among several types of investigations, we include calculations showing how the frequency resolution of the continuous spectrum affects the transport distance between a discrete and a continuous spectrum. We also use the transport distance to measure the distance between a continuous experimental electronic absorption spectrum of SO2 and a theoretical stick spectrum for the same system. The comparison of the theoretical and experimental SO2 spectra also allows us to suggest a theoretical value for the band origin that is closer to the observed band origin than previous theoretical values.

Coordination of new palladium (II) complexes with derived furopyran-3,4‑dione ligands: Synthesis, characterization, redox behaviour, DFT, antimicrobial activity, molecular docking and ADMET studies

The synthesis, characterization, theoretical study, electrochemical behaviour and biological activity of new series of Pd (II) complexes were reported with 6-methyl-2-(phenyl(p-tolylamino)methyl)-4H-furo[3,2-c]pyran-3,4(2H)-dione derived ligands. [MLCl2] is the proposed general formula of complexes. The synthesized complexes were prepared and experimentally characterized by elemental analysis, SEM-EDX, FTIR, 1HNMR, UV-Visible spectroscopy, magnetic measurement, conductivity and thermal analysis. FTIR spectroscopy has revealed the coordination mode of complexes through nitrogen and oxygen atoms. The Density Functional Theory calculation was applied to optimize the geometric structure of complexes, whereas Orbital Molecular Frontiers calculations allowed to define their stability. The experimental electronic spectra and magnetic measurement results approved a square planar geometry for all complexes. These results correlate with theoretical calculations. The electrochemical behaviour of ligands and complexes were determined by cyclic voltammetry, which reveal different redox processes of Pd (II) couples for the three complexes. The antimicrobial activity of all compounds was evaluated against different micro-organisms using agar disc-diffusion method. Most of compounds exhibit a remarkable inhibition against standard yeasts and S. aureus Gram positive bacteria. The ADMET study was carried out to predict pharmacokinetic and toxicity of synthesised compounds. Molecular Docking of HL3 and Pd-HL3 against S. aureus was applied in order to study their molecular interactions.

Rationalizing the Fluorescence Behavior of Core-Substituted Naphthalene Diimides

We study the internal conversion (IC) and intersystem crossing (ISC) pathways of low-lying excited electronic states of three core-substituted naphthalene diimides (bNDI, yNDI, and gNDI) using wavepacket simulations within the linear vibronic coupling method. Our wavepacket simulations reproduce the experimental electronic absorption spectra very well. All molecules decay rapidly to S2 upon populating a higher dipole-allowed singlet excited-state. The S2 → S1 IC dynamics and singlet-triplet energy gap, spin-orbit coupling strength trends suggest a favorable S2 → T4 ISC in gNDI. The efficient ultrafast T4 formation and its decay to lower triplet states make gNDI nonfluorescent. Such triplet formation pathways are not operative in both bNDI and yNDI; hence, these molecules emit fluorescence from S1 after a slower S2 → S1 IC.

New Isoquinoline Alkaloids from Paraphaeosphaeria sporulosa F03, a Fungal Endophyte Isolated from Paepalanthus planifolius.

As part of our continuing efforts to discover new bioactive compounds from endophytic fungal sources, we have investigated the extract of the Paraphaeosphaeria sporulosa F03 strain. The study led to the isolation of four new 3-methyl-isoquinoline alkaloids (1: - 4: ) and four known polyketides (5: - 8: ). The structures of compounds 1: - 4: were elucidated by 1D and 2DNMR experiments and HRMS analysis. The absolute configuration of 4: was determined by comparison of its experimental electronic circular dichroism spectrum with calculated data. Compounds 1: - 4: exhibited antifungal activity with minimal inhibitory concentration values ranging from 6.25 - 50 µg/mL against six Candida species but they did not present any cytotoxic activity against the human tumor cell lines A549 (lung), MCF-7 (breast), and HepG2 (hepatocellular). In addition, compound 4: exhibited antiplasmodial activity in the low micromolar range (IC50 = 4 µM).