How generic is iodide-tagging photoelectron spectroscopy: An extended investigation on the Gly·X- (Gly = glycine, X = Cl or Br) complexes.

We report a joint negative ion photoelectron spectroscopy (NIPES) and quantum chemical computational study on glycine-chloride/bromide complexes (denoted Gly·X-, X = Cl/Br) in close comparison to the previously studied Gly·I- cluster ion. Combining experimental NIPE spectra and theoretical calculations, various Gly·X- complexes were found to adopt the same types of low-lying isomers, albeit with different relative energies. Despite more congested spectral profiles for Gly·Cl- and Gly·Br-, spectral assignments were accomplished with the guidance of the knowledge learned from Gly·I-, where a larger spin-orbit splitting of iodine afforded well-resolved, recognizable spectral peaks. Three canonical plus one zwitterionic isomer for Gly·Cl- and four canonical conformers for Gly·Br- were experimentally identified and characterized in contrast to the five canonical ones observed for Gly·I- under similar experimental conditions. Taken together, this study investigates both genericity and variations in binding patterns for the complexes composed of glycine and various halides, demonstrating that iodide-tagging is an effective spectroscopic means to unravel diverse ion-molecule binding motifs for cluster anions with congested spectral bands by substituting the respective ion with iodide.

Synthesis, and biological evaluation of pyrazole matrine derivatives as an insecticide against Spodoptera frugiperda.

As one of the major threats to global food security, Spodoptera frugiperda (S. frugiperda) is highly gaining consideration due to its severe damage. Matrine is a widely and effectively used botanical insecticide in controlling S.frugiperda but lacks a rapidly available effect. To further improved the insecticidal activity of matrine based on combination principles, this work synthesized five new pyrazole matrine derivatives (PMDs) using Michael addition and investigated insecticidal activity against 2nd instar larvae of S. frugiperda(in vivo) and its isolated cell(in vitro). Our result demonstrated that PMDs show higher pesticidal activity than that matrine in both in vitro and in vivo assays. The most toxic derivatives in vitro and in vivo are PMD-3 and PMD-1, with IC50 of 2.49 mM and LC50 of 22.76 mg/L respectively. This research also investigates the anti-proliferation mechanism of PMDs based on isolated cells. PMDs decrease mitochondria membrane potential, arrested cell cycle at the G2/M phase, and upregulated Caspase 3, Caspase 9, and Apaf-1 to induce Caspase-dependent apoptosis. For Caspase-independent apoptosis, AIF and Endo G were found to be upregulated. Besides, pro-apoptotic factors like p53, IBM-1, and anti-apoptotic factors like IAP were upregulated. Moreover, we supposed that there was a linkage between lysosomes and PMD-induced apoptosis according to increased apoptosis rate, activated lysosomes, and upregulated Cathepsin B. This research provides new ideas for the synthesis of matrine derivatives and further demonstrated the anti-proliferation mechanism of PMDs.

RecT Affects Prophage Lifestyle and Host Core Cellular Processes in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a notorious pathogen that causes various nosocomial infections. Several prophage genes located on the chromosomes of P. aeruginosa have been reported to contribute to bacterial pathogenesis via host phenotype transformations, such as serotype conversion and antibiotic resistance. However, our understanding of the molecular mechanism behind host phenotype shifts induced by prophage genes remains largely unknown. Here, we report a systematic study around a hypothetical recombinase, Pg54 (RecT), located on a 48-kb putative prophage (designated PP9W) of a clinical P. aeruginosa strain P9W. Using a ΔrecT mutant (designated P9D), we found that RecT promoted prophage PP9W excision and gene transcription via the inhibition of the gene expression level of pg40, which encodes a CI-like repressor protein. Further transcriptomic profiling and various phenotypic tests showed that RecT modulated like a suppressor to some transcription factors and vital genes of diverse cellular processes, providing multiple advantages for the host, including cell growth, biofilm formation, and virulence. The versatile functions of RecT hint at a strong impact of phage proteins on host P. aeruginosa phenotypic flexibility. IMPORTANCE Multidrug-resistant and metabolically versatile P. aeruginosa are difficult to eradicate by anti-infective therapy and frequently lead to significant morbidity and mortality. This study characterizes a putative recombinase (RecT) encoded by a prophage of a clinical P. aeruginosa strain isolated from severely burned patients, altering prophage lifestyle and host core cellular processes. It implies the potential role of RecT in the coevolution arm race between bacteria and phage. The excised free phages from the chromosome of host bacteria can be used as weapons against other sensitive competitors in diverse environments, which may increase the lysogeny frequency of different P. aeruginosa subgroups. Subsequent analyses revealed that RecT both positively and negatively affects different phenotypic traits of the host. These findings concerning RecT functions of host phenotypic flexibility improve our understanding of the association between phage recombinases and clinical P. aeruginosa, providing new insight into mitigating the pathogen infection.

Characteristics of Wild Bird Resistomes and Dissemination of Antibiotic Resistance Genes in Interconnected Bird-Habitat Systems Revealed by Similarity of blaTEM Polymorphic Sequences.

Wild birds are known to harbor and discharge antibiotic-resistant bacteria (ARB) and their associated antibiotic resistance genes (ARGs). However, assessments of their contribution to the dissemination of antibiotic resistance in the environment are limited to culture-dependent bacterial snapshots. Here, we present a high-throughput sequencing study that corroborates extensive ARG exchange between wild bird feces and their habitats and implies the need to scrutinize high-mobility birds as potential vectors for global propagation of ARGs. We characterized the resistome (281 ARGs) and microbiome of seven wild bird species and their terrestrial and aquatic habitats. The resistomes of bird feces were influenced by the microbial community structure, mobile genetic elements (MGEs), and residual antibiotics. We designated 33 ARGs found in more than 90% of the bird fecal samples as core ARGs of wild bird feces, among which 16 ARGs were shared as core ARGs in both wild bird feces and their habitats; these genes represent a large proportion of both the bird feces (35.0 ± 15.9%) and the environmental resistome (29.9 ± 21.4%). One of the most detected ß-lactam resistance genes (blaTEM, commonly harbored by multidrug resistant "superbugs") was used as molecular marker to demonstrate the high interconnectivity of ARGs between the microbiomes of wild birds and their habitats. Overall, this work provides a comprehensive analysis of the wild bird resistome and underscores the importance to consider genetic exchange between animals and the environment in the One Health approach.

Synthesis of Halopyrazole Matrine Derivatives and Their Insecticidal and Fungicidal Activities.

Matrine is a traditional botanical pesticide with a broad-spectrum biological activity that is widely applied in agriculture. Halopyrazole groups are successfully introduced to the C13 of matrine to synthesize eight new derivatives with a yield of 78-87%. The insecticidal activity results show that the introduction of halopyrazole groups can significantly improve the insecticidal activity of matrine on Plutella xylostella, Mythimna separata and Spodoptera frugiperda with a corrected mortality rate of 100%, which is 25-65% higher than matrine. The fungicidal activity results indicate that derivatives have a high inhibitory effect on Ceratobasidium cornigerum, Cibberella sanbinetti, Gibberrlla zeae and Collectot tichum gloeosporioides. Thereinto, 4-Cl-Pyr-Mat has the best result, with an inhibition rate of 23-33% higher than that of matrine. Therefore, the introduction of halogenated pyrazole groups can improve the agricultural activity of matrine.

Spectroscopic evidence for intact carbonic acid stabilized by halide anions in the gas phase.

This work shows elusive carbonic acid being effectively stabilized in the gas phase by interacting with halide anions X- (X = F, Cl, Br, and I). The formed H2CO3·X- complexes, characterized by negative ion photoelectron spectroscopy and ab initio calculations, all contain intact trans-trans carbonic acid binding onto the respective halide via two identical strong ionic O-HX- hydrogen bonds. For X = Cl, Br, and I, the complex spectra exhibit the corresponding X- signature by simply shifting to the higher binding energy side, while an extremely 2 eV wide broader band is observed for X = F. This spectroscopic evidence indicates that an excess electron is removed from each halide in the former case, while a proton is transferred from carbonic acid to fluoride upon electron detachment for the latter. The above H2CO3·X- structures as well as those of the previously studied H2SO4·X- along the homologous halogen series cannot be explained using the proton affinity (PA) argument. Instead, a qualitative correlation is found between these structural motifs and the constituent acid pKa values, strongly suggesting that pKa is a more suitable factor to predict correct acid-base chemistry between these diprotic oxyacids and halides.

Determinant Factor for Thermodynamic Stability of Sulfuric Acid-Amine Complexes.

Atmospheric amines are thought to play significant roles in the nucleation of sulfuric acid-mediated aerosol particles. Their enhancing effects on the stabilization of the related complexes have formerly been correlated with the amine base strength, but there are a few exceptions reported. In this work, the influence of seven alkylamines on the thermodynamic stability of sulfuric acid-amine complexes has been theoretically investigated, e.g., ethylamine, propylamine, isopropylamine, tert-butylamine, dimethylamine, ethylmethylamine, and trimethylamine. For all primary and secondary amine-mediated complexes, a dual hydrogen bond configuration is generally suggested in the most stable isomer. The stabilization of this special structure predicted by the electrostatic potential distribution on the molecular surface of amines exactly agrees with the base strength sequence, providing crucial evidence for the previous deduction of correlation between the base strength and the enhancing effect. Meanwhile, the considerable van der Waals interactions are found between the free hydroxyl of sulfuric acid and the ß-methyl group of amine, resulting in the extra stability for sulfuric acid-dimethylamine and sulfuric acid-ethylmethylamine complexes. Therefore, the electrostatic potential distribution of amines is the essential determinant factor for the thermodynamic stability of the relevant complexes. Our conclusions provide new insight into a way to evaluate the enhancing abilities of amines in aerosol particle nucleation.

Cl-Loss dynamics in the dissociative photoionization of CF3Cl with threshold photoelectron-photoion coincidence imaging.

The dissociative photoionization of CF3Cl was investigated in the photon energy range of 12.30-18.50 eV. The low-lying electronic states of CF3Cl+ cations were prepared by the method of threshold photoelectron-photoion coincidence (TPEPICO). The threshold photoelectron spectrum and the coincident time-of-flight mass spectra at the specific photon energies were recorded. Only a CF3+ fragment was observed at lower energy, while a CF2Cl+ fragment appeared for C2E and D2E states. As Cl-loss from the ground ionic state is statistical, the total kinetic energy release distribution (KERD) is represented as a Boltzmann profile, and a 0 K appearance energy of AP0 =12.79 ± 0.02 eV is derived from the statistical modelling of the breakdown diagram from 12.60 to 12.85 eV without taking into account the kinetic shift. For the A2A1 and B2A2 states of CF3Cl+ cations, the total KERDs are bimodal, where a parallel faster dissociation appears together with the statistical distribution. At higher energies like the C2E and D2E ionic states, a bimodal distribution similar to that of the A2A1 and B2A2 states is also observed for the KERD. With the aid of the calculated Cl-loss potential energy curves, the dissociative mechanisms of internal energy-selected CF3Cl+ cations are proposed.

Effective identification of essential proteins based on priori knowledge, network topology and gene expressions.

Identification of essential proteins is very important for understanding the minimal requirements for cellular life and also necessary for a series of practical applications, such as drug design. With the advances in high throughput technologies, a large number of protein-protein interactions are available, which makes it possible to detect proteins' essentialities from the network level. Considering that most species already have a number of known essential proteins, we proposed a new priori knowledge-based scheme to discover new essential proteins from protein interaction networks. Based on the new scheme, two essential protein discovery algorithms, CPPK and CEPPK, were developed. CPPK predicts new essential proteins based on network topology and CEPPK detects new essential proteins by integrating network topology and gene expressions. The performances of CPPK and CEPPK were validated based on the protein interaction network of Saccharomyces cerevisiae. The experimental results showed that the priori knowledge of known essential proteins was effective for improving the predicted precision. The predicted precisions of CPPK and CEPPK clearly exceeded that of the other 10 previously proposed essential protein discovery methods: Degree Centrality (DC), Betweenness Centrality (BC), Closeness Centrality (CC), Subgraph Centrality (SC), Eigenvector Centrality (EC), Information Centrality (IC), Bottle Neck (BN), Density of Maximum Neighborhood Component (DMNC), Local Average Connectivity-based method (LAC), and Network Centrality (NC). Especially, CPPK achieved 40% improvement in precision over BC, CC, SC, EC, and BN, and CEPPK performed even better. CEPPK was also compared to four other methods (EPC, ORFL, PeC, and CoEWC) which were not node centralities and CEPPK was showed to achieve the best results.

[Non-covalent albumin conjugates of silicon (IV) phthalocyanines axially substituted with nucleoside: preparation and in vitro photodynamic activities].

The interactions of bovine serum albumin (BSA) with five novel silicon (N) phthalocyanines(SiPcl-5) axially modified by nucleosides (cytidine, 5-N-cytidine, methyl cytidine, uridine and methyl uridine) derivatives were studied by fluorescence spectroscopy. The results show that there are strong interactions between these silicon phthalocyanines and BSA with a binding constant of (4.90-83.18) x 10(5) mol(-1) x L. Therefore, the non-covalent BSA conjugate of bis(2', 3'-O-isopropyl-cytidine-oxy) phthalocyaninatosilicon(IV) (SiPc1) was further been prepared. The molar ratio of phthalocyanine to albumin was found to be 1:1 for the obtained SiPcl-BSA conjugate. The absorption spectra of SiPc1 and SiPc1-BSA in the visible region have no significant difference, both showing an Q-band maximum at about 686 nm. It indicates that the spectroscopic characteristics of SiPc1 are not affected by binding to albumin. The SiPcl-BSA conjugate exhibits high photodynamic activity against human hepatoma cell line HepG2 with an IC50 value of 3.0 x 10(-7) mol x L(-1). By comparsion, SiPc1-BSA has a higher photodynamic activity than SiPc1 (in PBS formation, IC50 = 7.0 x 10(-7) mol x L(-1)), which can be attributed to its higher cellular uptake.

Photodetachment photoelectron spectroscopy shows isomer-specific proton-coupled electron transfer reactions in phenolic nitrate complexes.

The oxidation of phenolic compounds is one of the most important reactions prevalent in various biological processes, often explicitly coupled with proton transfers (PTs). Quantitative descriptions and molecular-level understanding of these proton-coupled electron transfer (PCET) reactions have been challenging. This work reports a direct observation of PCET in photodetachment (PD) photoelectron spectroscopy (PES) of hydrogen-bonded phenolic (ArOH) nitrate (NO3-) complexes, in which a much slower rising edge provides a spectroscopic signature to evidence PCET. Electronic structure calculations unveil the PCET processes to be isomer-specific, occurred only in those with their HOMOs localized on ArOH, leading to charge-separated transient states ArOH•+·NO3- triggered by ionizing phenols while simultaneously promoting PT from ArOH•+ to NO3-. Importantly, this study showcases that gas-phase PD-PES is a generic means enabling to identify PCET reactions with explicit structural and binding information.

Preparation of High Vibrational States in the Entire Molecular Beam.

Preparing highly excited molecules is of great interest in chemistry, but it has long been a challenge due to the high laser power required within the narrow line width to excite a weak transition. We present a cavity-enhanced infrared excitation scheme using a milliwatt laser. As a demonstration, about 35% of CO molecules in a ground-state rotational level were excited to the highly excited v = 3 state in the entire pulsed supersonic beam, as confirmed by the depletion of molecules in the ground state. The method was also applied to excite HD molecules to the v = 2 state with a continuous-wave diode laser. This work provides a universal approach to prepare molecules in a specific quantum state, paving the way to study the chemical reaction dynamics of highly excited molecules.

Inter-plasmid transfer of antibiotic resistance genes accelerates antibiotic resistance in bacterial pathogens.

Antimicrobial resistance is a major threat for public health. Plasmids play a critical role in the spread of antimicrobial resistance via horizontal gene transfer between bacterial species. However, it remains unclear how plasmids originally recruit and assemble various antibiotic resistance genes (ARGs). Here, we track ARG recruitment and assembly in clinically relevant plasmids by combining a systematic analysis of 2420 complete plasmid genomes and experimental validation. Results showed that ARG transfer across plasmids is prevalent, and 87% ARGs were observed to potentially transfer among various plasmids among 8229 plasmid-borne ARGs. Interestingly, recruitment and assembly of ARGs occur mostly among compatible plasmids within the same bacterial cell, with over 88% of ARG transfers occurring between compatible plasmids. Integron and insertion sequences drive the ongoing ARG acquisition by plasmids, especially in which IS26 facilitates 63.1% of ARG transfer events among plasmids. In vitro experiment validated the important role of IS26 involved in transferring gentamicin resistance gene aacC1 between compatible plasmids. Network analysis showed four beta-lactam genes (blaTEM-1, blaNDM-4, blaKPC-2, and blaSHV-1) shuffling among 1029 plasmids and 45 clinical pathogens, suggesting that clinically alarming ARGs transferred accelerate the propagation of antibiotic resistance in clinical pathogens. ARGs in plasmids are also able to transmit across clinical and environmental boundaries, in terms of the high-sequence similarities of plasmid-borne ARGs between clinical and environmental plasmids. This study demonstrated that inter-plasmid ARG transfer is a universal mechanism for plasmid to recruit various ARGs, thus advancing our understanding of the emergence of multidrug-resistant plasmids.

Dissemination of antibiotic resistance genes from aboveground sources to groundwater in livestock farms.

Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are prevalent in various environments on livestock farms, including livestock waste, soil, and groundwater. Contamination of groundwater by ARB and ARGs in livestock farms is a growing concern as it may have potentially huge risks to human health. However, the source of groundwater-borne ARB and ARGs in animal farms remains largely unknown. In this study, different types of samples including groundwater and its potential contamination sources from aboveground (pig feces, wastewater, and soil) from both working and abandoned swine feedlots in southern China were collected and subjected to metagenomic sequencing and ARB isolation. The source tracking based on metagenomic analysis revealed that 56-95 % of ARGs in groundwater was attributable to aboveground sources. Using metagenomic assembly, we found that 45 ARGs predominantly conferring resistance to aminoglycosides, sulfonamides, and tetracyclines could be transferred from the aboveground sources to groundwater, mostly through plasmid-mediated horizontal gene transfer. Furthermore, the full-length nucleotide sequences of sul1, tetA, and TEM-1 detected in ARB isolates exhibited the close evolutionary relationships between aboveground sources and groundwater. Some isolated strains of antibiotic-resistant Pseudomonas spp. from aboveground sources and groundwater had the high similarity (average nucleotide identity > 99 %). Notably, the groundwater-borne ARGs were identified as mainly carried by bacterial pathogens, potentially posing risks to human and animal health. Overall, this study underscores the dissemination of ARGs from aboveground sources to groundwater in animal farms and associated risks.

[Synthesis and photodynamic anticancer activity of silicon phthalocyanine axially modified by nucleoside derivatives].

A new axially modified silicon phthalocyanine, di [5'-(2', 3'-O-isopropyl)-5-methyl cytidineoxy] silicon phthalocyanine (SiPcG), was prepared and characterized by 1H NMR and HRMS. This compound is essentially nonaggregated in N,N-dimethyformamide and 1% cremophor EL aqueous solution. It shows a Qband at 676 nm and fluorescence emission at 685 nm in DMF, and exhibits a Q-band at 679 nm and fluorescence emission at 689 nm in 1% cremophor EL aqueous solution. The SiPcG shows a high photodynamic activity against human hepatoma cells HepG2 with an IC50 value down to 7.8 x 10(-8) mol x L(-1). Fluorescence confocal microscopy study indicated that the SiPcG locates preferentially in the mitochondria of cells. The research results show that the SiPcG is highly potential as a new anti-cancer photosensitizer.

[Spectral properties, photodynamic anticancer activity and the interaction with albumin of silicon phthalocyanine axially modified by pyrimidine derivatives].

Photophysical photochemical properties, in vitro photodynamic anticancer activity and interaction with albumin of a new axially modified silicon phthalocyanine, i. e. di (2-amino-6-trifluoromethyl-4-pyrimidinyloxy) silicon phthalocyanine (SiPcF), were studied in the present paper. The Q band maximum absorption of SiPcF located at 686 nm with the molar absorption coefficient of 2.3 x 10(5) mol(-1) * L * cm(-1). The fluorescence emission of SiPcF peaked at 694 nm with a fluorescence quantum yield of 0.46. Its singlet oxygen quantum yield produced by photosensitization is 0.38, suggesting that SiPcF is an effective 1O2 photosensitizer. There is strong interaction between SiPcF and bovine serum albumin (BSA). The binding constant is 4.33 x 10(5) mol X L(-1) and the number of binding sites is 1. In vitro experiments show that SiPcF had a high photodynamic anticancer activity against human hepatoma cells HepG2 with an IC50 value down to 5 x 10(-7) mol X L(-1).

Global Increase of Antibiotic Resistance Genes in Conjugative Plasmids.

Antibiotic resistance is propagating worldwide, but the predominant dissemination mechanisms are not fully understood. Here, we report that antibiotic resistance gene (ARG) abundance in conjugative plasmids that are recorded in the National Center for Biotechnology Information (NCBI) RefSeq plasmid database is increasing globally, which is likely a key factor in the propagation of resistance. ARG abundance in plasmids increased by 10-fold on a global scale from the year 2000 to the year 2020 (from 0.25 to 2.93 ARG copies/plasmid), with a more pronounced increase being observed in low-to-middle income countries. This increasing trend of plasmid-borne ARGs was corroborated by bootstrap resampling from each year of the NCBI RefSeq plasmid database. The results of a correlation analysis imply that if antibiotic consumption keeps growing at the current rates, a 2.7-fold global increase in the ARG abundance of clinically relevant plasmids may be reached by 2030. High sequence similarities of clinically relevant, conjugative plasmids that are isolated both from clinics and from the environment raise concerns about the environmental resistome serving as a potential ARG maintenance reservoir that facilitates transmission across these ecological boundaries. IMPORTANCE Antibiotic resistance propagation is a significant concern due to its projected impacts on both global health and the economy. However, global propagation mechanisms are not fully understood, including regional and temporal trends in the abundance of resistance plasmids that facilitate antibiotic resistance gene (ARG) dissemination. This unprecedented study reports that ARG abundance in the conjugative plasmids that are recorded in the National Center for Biotechnology Information (NCBI) database and harbor ARGs is increasing globally with antibiotic consumption, especially in low-to-medium income countries. Through network and comparative genomic analyses, we also found high sequence similarities of clinically relevant conjugative resistance plasmids that were isolated from clinical and environmental sources, suggesting transmission between these ecological boundaries. Therefore, this study informs the One Health perspective to develop effective strategies by which to curtail the propagation of plasmid-borne antibiotic resistance.

Effects of a chitosan nanoparticles encapsulation on the properties of litchi polyphenols.

Litchi polyphenols have very specific biological activities. Nevertheless, the low and inconsistent oral bioavailability and instability hinder the further application of litchi polyphenols in food systems. This work prepared litchi polyphenols loaded chitosan nanoparticles (LP-CSNPs) by ionic gelation method to enhance the encapsulation on the properties of litchi polyphenols. The optimum conditions of formation via single factors and the Box-Behnken design were chitosan (CS) concentration 1.065 mg/mL, sodium tripolyphosphate (TPP) concentration 0.975 mg/mL, and the mass ratios of polyphenols and CS 1:1 with encapsulation efficiency (EE%) of 45.53%. LP-CSNPs presented the nanosized range of particle size (mean 170 nm), excellent polydispersity index (PDI) (0.156 ± 0.025), and zeta potential values (+ 35.44 ± 0.59). The in vitro release in simulated gastric fluid (pH 1.2) and intestinal fluid (pH 6.8) during 100 h was 58.34% and 81.68%, respectively. LP-CSNPs could effectively improve the storage stability and had great antibacterial activity compared with unencapsulated litchi polyphenols.

[Synthesis, structure and special study of 1D cadmium sulfate-H2biim coordination polymer].

A novel cadmium complexes of {[Cd(H2 biim)2 (SO4)] x 3H2O}n(1) (H2 biim = 2,2'-biimidazole) was synthesized by hydrothermal reaction of 3CdSO4 x 8H2O and 2,2'-biimidazole ligand. The complex was built up by [Cd(H2 biim)2]2+ units bridged sequentially by SO4(2-) anions to form 1D zigzag chains parallel to the c-axis. The H2biim ligands were attached to the 1D chain as branches of the chain by coordinating to Cd2+ at two sides of the chain. The chains were held together by pi--pi interaction and O--H***O interactions, thus yielding a 3D extended supramolecular network The responses of symmetric stretching vibration of SO4(2-), N--C single bond, N==C double bond and anti-symmetric stretching vibration of N-C single bond were detected in 2D IR correlation spectra under thermal perturbation. The complex exhibited strong blue emission peak at 498 nm (lambda(ex) x = 397 nm) that can be assigned to a ligand-to-metal charge-transfer (LMCT) band.

[Structural and spectral study of a novel lanthanide 2-hydroxynicotinic acid coordination polymer].

A novel lanthanide 2-hydroxynicotinic acid coordination polymer 1 {[LaL(HL) (H2O)3]1/3 (SO4)2/3 (H3O)2 H2O} (H2 L = 2-hydroxynicotinic acid) has been synthesized under hydrothermal condition and characterized by crystal X-ray diffraction, IR, UV, TGA, two-dimensional infrared (2D IR) correlation spectroscopy with magnetic and thermal perturbation. In 1, La ions are connected by 2-hydroxynicotinic acid through both carboxylate oxygen atoms and oxygen atoms from hydroxyl group in pyridine to generate a 2D layer in the ab plane, these layers are further connected by weak interactions to form a 3D framework along c axis. The response of out-of-plane bending vibrations of N-H and C-H are remarkable in the 2D IR correlation spectra under magnetic perturbation, this may attributes to the inducement of pi-electron cloud deformation under magnetic perturbation, v4 vibrations from SO4(2-) was also sensitive to magnetic perturbation. In addition, stretching vibrations from N-H are sensitive to thermal perturbation.