Spectroscopic Methods Research Articles

Triazine Frameworks for the Photocatalytic Selective Oxidation of Toluene

AbstractInvestigations into the selective oxidation of inert sp3 C−H bonds using polymer photocatalysts under mild conditions have been limited. Additionally, the structure‐activity relationship of photocatalysts often remains insufficiently explored. Here, a series of thiophene‐based covalent triazine frameworks (CTFs) are used for the efficient and selective oxidation of hydrocarbons to aldehydes or ketones under ambient aerobic conditions. Spectroscopic methods conducted in situ and density functional theory (DFT) calculations revealed that the sulfur atoms within the thiophene units play a pivotal role as oxidation sites due to the generation of photogenerated holes. The effect of photogenerated holes on photocatalytic toluene oxidation was investigated by varying the length of the spacer in a CTF donor‐acceptor based photocatalyst. Furthermore, the manipulation of reactive oxygen species was employed to enhance selectivity by weakening the peroxidative capacity. As an illustrative example, this study successfully demonstrated the synthesis of a precursor of the neurological drug AMG‐579 using a photocatalytic protocol.

Triazine Frameworks for the Photocatalytic Selective Oxidation of Toluene.

Investigations into the selective oxidation of inert sp3 C-H bonds using polymer photocatalysts under mild conditions have been limited. Additionally, the structure-activity relationship of photocatalysts often remains insufficiently explored. Here, a series of thiophene-based covalent triazine frameworks (CTFs) are used for the efficient and selective oxidation of hydrocarbons to aldehydes or ketones under ambient aerobic conditions. Spectroscopic methods conducted in situ and density functional theory (DFT) calculations revealed that the sulfur atoms within the thiophene units play a pivotal role as oxidation sites due to the generation of photogenerated holes. The effect of photogenerated holes on photocatalytic toluene oxidation was investigated by varying the length of the spacer in a CTF donor-acceptor based photocatalyst. Furthermore, the manipulation of reactive oxygen species was employed to enhance selectivity by weakening the peroxidative capacity. As an illustrative example, this study successfully demonstrated the synthesis of a precursor of the neurological drug AMG-579 using a photocatalytic protocol.

Ternary Schiff base metal (II) complexes with N,N,N′,N′-Tetramethylethylenediamine: Influence of secondary chelates on antimicrobial, scavenging activity, DNA interaction and cytotoxicity

A series of complexes involving bivalent metal ions such as cobalt, nickel, copper, and zinc were synthesized using Schiff bases derived from l-tyrosine and salicylaldehyde. Utilizing both analytical and spectroscopic methods, the compounds underwent analysis. In terms of their potential biological effects, the antioxidant properties of the samples were gauged by their ability to scavenge DPPH radicals. Notably, all the compounds demonstrated enhanced activity in this aspect, with the exception of the ligand. To investigate their impact on DNA, the compounds' capability to cleave DNA was assessed via gel electrophoresis. Remarkably, the compounds effectively induced the cleavage of supercoiled plasmid DNA. Moreover, the interaction between calf thymus DNA and the metal-imine chelates were examined. The Cu(II) complex had a significant interaction, as evidenced by its binding constant of (3.46 ± 0.02 x 105 M−1).

Synthesis, crystal structure, Hirshfeld surface analysis, spectral characterisation, non-covalent interactions and anti-microbial investigation on morpholinium adipate: a combined experimental and DFT approach

MPAA was synthesised and evaluated using spectroscopic methods and quantum chemical computations in the proposed investigation. Extensive quantum chemical computations were employed to analyse FT-IR, FT-Raman and NMR spectra of molecule morpholinium adipate (MPAA). The results of a single crystal X-ray diffraction (SCXRD) experiment were compared with estimated structural characteristics. In conjunction with the scaled force constants, a comprehensive vibrational assignment is provided for the 96 anticipated vibration modes of MPAA. Charge transport inside the molecule is exposed by the band gap energy of 5.959 eV, which is the consequence of the predicted Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) values of −6.991 and −1.031 eV, respectively. The inter- and intramolecular H-bonding contacts in the molecule were studied using natural bond orbital analysis to learn more about the biological active site. The eventual charge transfer inside the molecule is supported by frontier molecular orbital analysis and natural bond orbital analysis. The anti-bonding of H15–O24 atoms and the lone pair N14 had the greatest stabilising energy at 16.52 kcal/mol. Using Hirshfeld surface analysis methods, intermolecular connections and crystal packing of MPAA are investigated. The fukui and electrostatic potential plot analyses can provide information about the molecule’s electrophilic and nucleophilic locations. Antimicrobial tests have been performed to see how well the chemical worked against various bacterial and fungal strains. Docking of 8OEO (Aspergillus Niger), 7C2O (Candida parapsilosis), 2O6I (Enterococcus faecalis) and 1DZO (Pseudomonas aeruginosa) proteins has been done, and lowest binding energy −4.57 kcal/mol has been achieved for 7C2O protein.

A disaggregation-driven BODPIY-based probe for ratiometric detection of G4 DNA

In conventional systems, fluorescent probes with planar structures usually experience the phenomenon of aggregation-induced quenching (ACQ) that limits their practical applications in bio-medical sensing. To confront such problem, an attractive way is to develop a disaggregation-induced emission (DIE) sensing strategy, where the quenched fluorescence is recovered via a disaggregation process. Currently most of the fluorescent probes designed based on DIE mechanism are signal off-on type with the fluorescent intensity changed at a single wavelength. On the other hand, ratiometric fluorescent probes have the advantage of having two distinct emission wavelengths, effectively avoiding environmental interference. The DIE probes with a ratiometric fluorescence response still poorly established. Herein, we report a BODIPY-based probe BODPA, where a 2,2′-dipicolylamine group was introduced to the meso-position of BODIPY core, for the selective ratiometric detection of G-quadruplex (G4) DNA. This probe in buffer solution formed aggregates with weak fluorescence at 508 nm. In the presence of G4 DNA, bright fluorescence was emitted at 518 nm through DIE mechanism. Taking advantage of the ratiometric manner, probe BODPA exhibited selectivity for G4 DNA over duplex DNA. The binding details between probe BODPA and G4 DNA were assessed by spectroscopic and molecular modeling methods, which suggested the ability of this probe could coordinate with G4 structure via end stacking and partial groove binding mode.

Complex formation of ML324, the histone demethylase inhibitor, with essential metal ions: Relationship between solution chemistry and anticancer activity

N-(3-(dimethylamino)propyl-4-(8-hydroxyquinolin-6-yl)benzamide (ML324, HL) is a potent inhibitor of the iron-containing histone demethylase KDM4, a recognized potential target of cancer therapeutics. Herein, we report the proton dissociation and complex formation processes of ML324 with essential metal ions such as Fe(II), Fe(III), Cu(II) and Zn(II) using UV–visible, fluorescence, electron paramagnetic resonance and 1H NMR spectroscopic methods. The electrochemical behaviour of the copper and iron complexes was characterized by cyclic voltammetry and spectroelectrochemistry. The solid phase structure of ML324 analysed by X-ray crystallography is also provided. Based on the solution equilibrium data, ML324 is present in solution in H2L+ form with a protonated dimethylammonium moiety at pH 7.4, and this (N,O) donor bearing ligand forms mono and bis complexes with all the studied metal ions and the tris-ligand species is also observed with Fe(III). At pH 7.4 the metal binding ability of ML324 follows the order: Fe(II) < Zn(II) < Cu(II) < Fe(III). Complexation with iron resulted in a negative redox potential (E'1/2 = −145 mV vs. NHE), further suggesting that the ligand has a preference for Fe(III) over Fe(II). ML324 was tested for its anticancer activity in chemosensitive and resistant human cancer cells overexpressing the efflux pump P-glycoprotein. ML324 exerted similar activity in all tested cells (IC50 = 1.9–3.6 μM). Co-incubation and complexation of the compound with Cu(II) and Zn(II) had no impact on the cytotoxicity of ML324, whereas Fe(III) decreased the toxicity in a concentration-dependent manner, and this effect was more pronounced in the multidrug resistant cells.

Halogenated Cyclic Monoterpenoids with Anti-Biofouling Activity from the Okinawan Red Marine Algae Portieria Hornemannii.

The red algal genus Portieria is a prolific producer of halogenated monoterpenoids. In this study, we isolated and characterised monoterpenoids from the Okinawan red algae Portieria hornemannii. A new polyhalogenated cyclic monoterpenoid, 2(R)-chloro-1,6(S)-dibromo-3(8)(Z)-ochtoden-4(R)-ol (1), along with three known monoterpenoids, (2R,3(8)E,4S,6R)-6-bromo-2-chloro-1,4-oxido-3(8)-ochtodene (2), 1-bromo-2-chloroochtoda-3(8),5-dien-4-one (3), and 2-chloro-1-hydroxyochtoda-3(8),5-dien-4-one (4) were isolated from the methanol extract of three populations of P. hornemannii. These compounds were characterised using a combination of spectroscopic methods and chemical synthesis, and the absolute stereochemistry of compounds 1 and 2 was determined. In addition, all isolated compounds were screened for their anti-biofouling activity against the mussel Mytilus galloprovincialis, and 1 exhibited strong activity. Therefore, halogenated monoterpenoids have the potential to be used as natural anti-biofouling drugs.

Optimization and Applications of Instrumental and Preconcentration Neutron Activation Analysis Methods for Rapid Determination of Selected REE by Utilizing their Short‐Lived Activation Products**

AbstractDetermination of Rare Earth Elements (REEs) using spectroscopic methods is challenging. Conventional Instrumental Neutron Activation Analysis (INAA) method utilizing Pneumatic Carrier Facility (PCF) of Dhruva research reactor has been optimized with the short‐lived isotopes such as 161Gd, 165mDy and 153/155Sm for quantification of Gd, Dy and Sm respectively. Such isotopes are difficult to observe by conventional INAA with longer cooling periods owing to their very short half‐lives (1–3 mins). In this work, such isotopes are not only observed but also utilized as activation product for rapid determination of these REEs. The standardized method has been utilized for the first time in liquid samples involving nuclear fuel like U3O8 wherein TBP/n‐dodecane has been applied for chemical separation of Uranium prior to analysis. The INAA method has also been applied for validating the stoichiometry of Gd in Gd3+ co‐doped Zn2P2O7:Tb3+ green emitting solid‐state phosphors, which plays a very pivotal role in sensitizing the terbium ion in its performance for solid state lighting. We believe with huge current demand of REEs in research, science and technology; INAA can be a game changer wherever needed for quantification with high precision and accuracy and can also be extended to other REEs of interest.

Phytochemical Investigation and Biological Studies of Coffea benghalensis B. Heyne Ex Schult

The qualitative phytochemical screening of leaves and stems of Coffea benghalensis B. Heyne Ex Schult showed the presence of saponins, flavonoids, steroids, and cardiac glycoside. Stigmasterol, 1, 3- stearyl-oleyl-glyceride and stigmasterol glucoside were isolated and characterized from the dichloromethane extract of this plant leaves and stems by chromatographic and spectroscopic methods. Total caffeine content per hundred grams was estimated. Fatty acids were analyzed quantitatively by GLC. Total antioxidant capacity and antimicrobial activity of the plant leaves and stems extract were studied. Dhaka Univ. J. Sci. 72(1): 92-97, 2024 (January)

A Photoswitchable Metallocycle Based on Azobenzene: Synthesis, Characterization, and Ultrafast Dynamics.

The novel photoswitchable ligand 3,3'-Azobenz(metPA)2 (1) is used to prepare a [Cu2(1)2](BF4)2 metallocycle (2), whose photoisomerization was characterized using static and time-resolved spectroscopic methods. Optical studies demonstrate the highly quantitative and reproducible photoinduced cyclic E/Z switching without decay of the complex. Accordingly and best to our knowledge, [Cu2(1)2](BF4)2 constitutes the first reversibly photoswitchable (3d)‑metallocycle based on azobenzene. The photoinduced multiexponential dynamics in the sub-picosecond to few picosecond time domain of 1 and 2 have been assessed. These ultrafast dynamics as well as the yield of the respective photostationary state (PSSZ = 65%) resemble the behavior of archetypical azobenzene. Also, the innovative pump-probe laser technique of gas phase transient photodissociation (t-PD) in a mass spectrometric ion trap was used to determine the intrinsic relaxation dynamics for the isolated complex. These results are consistent with the results from femtosecond UV/Vis transient absorption (fs-TA) in solution, emphasizing the azobenzene-like dynamics of 2. This unique combination of fs-TA and t-PD enables valuable insights into the prevailing interplay of dynamics and solvation. Both analyses (in solution and gas phase) and quantum chemical calculations reveal a negligible effect of the metal coordination on the switching mechanism and electronic pathway, which suggests a non-cooperative isomerization process.

Corrosion inhibition performance of new Schiff base cyclohexanamine derivatives on C-steel in 1 M HCl solution: Electrochemical, chemical, surface and computational explorations

Iron has many advantages, which makes it a material of great importance on the industrial level, but it is quickly affected by surrounding environmental factors that cause its corrosion. In this context, two new Schiff base cyclohexanamine derivatives (CSBs) were synthesized, characterized, and screened as corrosion inhibitors of C-steel in a 1 M hydrochloric acid solution. Specifically, they are (Z)-N-cyclohexyl-1-phenylethan-1-imine (CSB-1) and (E)-N′-cyclohexyl-N-hydroxybenzimidamide (CSB-2). 1H NMR was used to determine the structures of the new CSB molecules. The inhibition efficacies (%IE) were evaluated by combining theoretical, physical, chemical, electrochemical, and spectroscopic methods. The results confirmed that CSBs were mixed-type inhibitors and that the IE depended linearly on their concentration. The adsorption of these molecules on the metal surface is key to this role. Kinetic and thermodynamic studies indicated that they are physically adsorbed and subject the Langmuir adsorption isotherm. Using 0.001 M of inhibitor, the maximum %IEs achieved were 91.1 % for CSB-1 and 94.4 % for CSB-2, respectively, which confirms tatehat they are promising inhibitors. Surface analysis via atomic force microscopy (AFM) confirmed that the C-steel was covered in a protective layer. Several thermodynamic and kinetic parameters were calculated. DFT and Mullikan charge calculations and molecular dynamics (MD) simulations were applied to predict the effectiveness and interactions of new CSBs on the steel surface as well. Theoretical expectations correspond to the practical.

A novel heterogeneous biocatalyst based on graphene oxide for synthesis of pyran derivatives

Graphene oxide modified with tryptophan (GO-Trp) has been introduced as a new heterogeneous acid-base biocatalyst for synthesis of some pyran derivatives. GO was prepared according to the Hummer’s method and tryptophan as a low-cost green amino acid is covalently bonded to the surface of GO without any organic or toxic reagents in a green way. The new catalyst was characterized by different spectroscopic methods such as Fourier transform infrared, X-ray diffraction (XRD), etc. …. The results of XRD patterns showed an increase in the distance between the GO plates in the presence of the modifying agent which specifies the presence of amino acid between the GO layers. XPS analysis also confirmed successful modification through the presence of C–N bonds in the structure of the catalyst. In addition, improvements in thermal stability and changes in the morphology of the samples were observed using thermogravimetric analysis and Field emission scanning electron microscopy analysis respectively. Evaluation of the catalyst performance in the synthesis of some benzo[b]pyran and pyrano[3,2-c] chromene derivatives showed presentable results. Seven benzo[b]pyran (4a–4g) and five pyrano[3,2-c] chromene (4h–4l) derivatives were synthesized. GO-Trp as a safe, natural and efficient catalyst, could be reused up to 5 runs for synthesis of pyran derivatives without any significant decrease in its potency. High purity of the products and desirable yields are other points that make the present work more attractive.

Синтез и характеристика четырех новых карбоксилатных комплексов меди(II) с фрагментом адамантана

The paper considers the results of synthesis, elemental analysis, and spectroscopic methods (IR, UV-vis) of four new copper(II) complexes with anions of 1-adamantanecarboxylic acid, 4-(1-adamantyl)benzoic acid and their L-valine derivatives as ligands. Based on the obtained spectral data, the authors assumed the biyaderic structure of these complexes with bidentate coordination of carboxylate ligands of the type [Cu2+2(RCOO-)4(H2O)2], with RCOO-as carboxylate ligands. The synthesised compounds are of interest as low toxic potential therapeutic agents with anti-inflammatory and anti-cancer activity.

Synthesis and characteristics of four new copper(II) carboxylate complexes with adamantane fragment

The paper considers the results of synthesis, elemental analysis, and spectroscopic methods (IR, UV-vis) of four new copper(II) complexes with anions of 1-adamantanecarboxylic acid, 4-(1-adamantyl)benzoic acid and their L-valine derivatives as ligands. Based on the obtained spectral data, the authors assumed the biyaderic structure of these complexes with bidentate coordination of carboxylate ligands of the type [Cu2+2(RCOO-)4(H2O)2], with RCOO-as carboxylate ligands. The synthesised compounds are of interest as low toxic potential therapeutic agents with anti-inflammatory and anti-cancer activity.

Synthesis, characterization and revealing the sono-photochemical potential of new NIR BODIPY derivative

Although the idea of combining the light of photodynamic therapy (PDT) and the sound of sonodynamic therapy (SDT) and converting into a much more effective therapeutic treatment method, sonophotodynamic therapy (SPDT), is very wise and sensitizing agents such as phthalocyanines produce higher amounts of singlet oxygen (1O2) with this method, the usage of SPDT for boron-dipyrromethene (BODIPY)-based theranostics has put forward by our group for the first time and no studies have been published by other groups in the literature so far. Therefore, as our continuing motivation in this direction, in the present study, a novel near-infrared (NIR) BODIPY fluorophore bearing thienyl-pyridine substituent at meso-position, iodines as heavy atoms at 2-,6- positions and distyryl segments at 3-,5- positions which enlarge π-conjugation of the molecule has been synthesized successfully. The structural characterizations of the target NIR BODIPY2 has been accomplished by the conventional spectroscopic methods (1H NMR, 13C NMR, FT-IR (ATR), UV–Vis and HRMS/MS) and elemental analysis. In order to evaluate the singlet oxygen generation capacity of NIR BODIPY2, photochemical and sonophotochemical methods have been employed comparatively. The singlet oxygen quantum yield (ΦΔ) of NIR BODIPY2 was calculated 0.37 using by photochemical method, this value increased to 0.66 by sonophotochemical study. It can be said that these results will open new horizons for researchers in terms of understanding sonophotochemical measurements of BODIPY derivatives for future in vitro or in vivo studies.

Sub-PPB Detection with Gas-Phase Multiphoton Electron Extraction Spectroscopy under Ambient Conditions.

Multiphoton electron extraction spectroscopy (MEES) is an advanced analytical technique that has demonstrated exceptional sensitivity and specificity for detecting molecular traces on solid and liquid surfaces. Building upon the solid-state MEES foundations, this study introduces the first application of MEES in the gas phase (gas-phase MEES), specifically designed for quantitative detection of gas traces at sub-part per billion (sub-PPB) concentrations under ambient atmospheric conditions. Our experimental setup utilizes resonant multiphoton ionization processes using ns laser pulses under a high electrical field. The generated photoelectron charges are recorded as a function of the laser's wavelength. This research showcases the high sensitivity of gas-phase MEES, achieving high spectral resolution with resonant peak widths less than 0.02 nm FWHM. We present results from quantitative analysis of benzene and aniline, two industrially and environmentally significant compounds, demonstrating linear responses in the sub-PPM and sub-PPB ranges. The enhanced sensitivity and resolution of gas-phase MEES offer a powerful approach to trace gas analysis, with potential applications in environmental monitoring, industrial safety, security screening, and medical diagnostics. This study confirms the advantages of gas-phase MEES over many traditional optical spectroscopic methods and demonstrates its potential in direct gas-trace sensing in ambient atmosphere.

Synthesis and Characterization of Bisphenol-C Epoxy Crotonate and Its Fiber-Reinforced Composites

Bisphenol-C epoxy crotonate resin was synthesized by reacting 8.09g epoxy resin of bisphenol- C, and 2.15g crotonic acid using 25 mL 1,4-dioxane as a solvent, and 1 mL triethylamine as a catalyst at reflux temperature for 1-6 h. Solid epoxy crotonate (ECCR) is highly soluble in common organic solvents. ECCR was characterized by its acid (24.5-1.5 mg KOH/g) and hydroxyl (504.5-678.4 mg KOH/g) values. The structure of ECCR is supported by FTIR and 1HNMR spectroscopic methods. A DSC endothermic transition at 229oC indicated melting followed by thermal polymerization of ECCR. ECCR is thermally stable up to 320oC and follows three-step degradation kinetics. The first step followed first-order degradation kinetics, while the second and third steps followed one-half-order degradation kinetics. High values of kinetic parameters suggested the rigid nature of the crosslinked resin. Jute-, Glass- and Jute-natural fiber-ECCR composites showed moderate tensile strength, flexural strength, electric strength, and volume resistivity due to the rigid nature and poor interfacial adhesion of the composites. J-ECCR and G-ECCR composites showed high water absorption tendency and excellent hydrolytic stability against water, 10% aq. HCl and 10% aq. NaCl and even in boiling water. Mechanical and electrical properties and water absorption tendency of the composites indicated their usefulness as low load-bearing housing and insulating materials. They can also be utilized in harsh environmental conditions.

New heteroleptic l-argininato copper(II) complex with bromide and N, N’– heterocyclic ligands – synthesis, supramolecular, spectroscopic, magnetic and theoretical investigations

A new heteroleptic [CuBr(l−Arg)(bpy)]Br·2H2O (1) (l−Arg=l−Arginine, bpy=2,2’−bipyridine) complex has been synthesized and its molecular and supramolecular structure aspects have been discussed based on the X−ray single crystal structure and Hirshfeld analyses. In addition, the properties of complex 1 have been elucidated using different spectroscopic methods (FT−IR / FIR, Raman, NIR−Vis−UV, Q− / X− band EPR) and magnetic measurements. In this complex, the bromide anion occupies the apex of a slightly distorted square pyramid (τ = 0.12). The [CuBr(l−Arg)(bpy)]+ complex units exhibit a ribbon−like organization, with Cu(II) metal centers located at the corners of triangles where the shortest Cu∙∙∙Cu distance is 5.579 Å. The aromatic moieties of bpy are aligned nearly parallel leading to π···π interactions. Both, non−bonded and coordinated, Br− ions act as hydrogen−bond acceptors for guanidinium groups. Hirshfeld analysis indicated the importance of the Br∙∙∙H (17.9 − 18.4 %), O∙∙∙H (14.9−15.2 %), and H∙∙∙H (42.3−43.1 %) interactions in the molecular packing of the studied complex. Atoms in molecules (AIM) calculations indicated mainly the closed shell character for the Cu−N, Cu−O and Cu−Br coordination interactions. The G value calculated using the Q−band EPR spectra parameters g|| = 2.235 and g⊥= 2.05 is 4.7, what indicating negligible coupling and that local tetragonal axes are aligned parallel. A negative value of Weiss temperature θCW = -0.32 K indicates the presence of weak antiferromagnetic coupling between the neighboring Cu(II) ions mediated through hydrogen bonds and π-π stacking of aromatic moieties of bpy. The value of gav= 2.113 obtained from Q−band EPR spectra is consistent with that corresponding to the Curie constant (C = 0.4138 emu K mol−1), i.e.g = 2.101, and that obtained from the best fitting to the Brillouin function: g = 2.139.

Development of silver nanoparticle-chitosan composite film for determination of total antioxidant capacity of some fruit juices and plant extracts

In this study, a silver nanoparticle-chitosan (AgNPCh) composite film was developed for the determination of antioxidant capacity of polyphenolic compounds. The optimum conditions of solid nanosensor based on chitosan-based polymeric membranes containing AgNPs such as content of the composite film, pH and incubation time were idendified. The sensor measurement is based on the fact that the addition of polyphenols to the sample solution increases the absorption of Ag(0) NPs, which exhibit a characteristic plasmon absorption band at a wavelength of 423 nm and the developed method exhibits a linear variation versus the concentrations standard polyphenolic compounds. The method was applied to the apple, peach, cherry, grape and pomegranate juices and rosemary, marjoram and sage plant extracts. This sensor may be an alternative to conventional spectroscopic methods to design portable, low-cost, simple and easy-to-use field analyses without the need for special equipment for the determination of antioxidant capacity of polyphenolic compounds.

Conformer-Selective Photoelectron Circular Dichroism.

Conformational flexibility and chirality both play a key role in molecular recognition. It is therefore very useful to develop spectroscopic methods that simultaneously probe both properties. It has been theoretically predicted that photoelectron circular dichroism (PECD) should be very sensitive to conformational isomerism. However, experimental proof has been less forthcoming and only exists for a very few favorable cases. Here, we present a new PECD scheme based on resonance-enhanced two-photon ionization (RE2PI) using UV/Vis nanosecond laser excitations. The spectral resolution obtained thereby guarantees conformer-selectivity by inducing resonant conformer-specific ππ* S1←S0 transitions. We apply this experimental scheme to the study of chiral 1-indanol, which exists in two conformers linked by a ring inversion and defined by the position of the hydroxyl group, namely axial and equatorial. We show that the PECD of the equatorial and axial forms considerably differ in sign, magnitude and shape. We also discuss the influence of the total ionization energy, vibronic excitation of intermediate and final states, and relative polarization of the excitation and ionization lasers. Conformer-specificity adds a new dimension to the applications of PECD in analytical chemistry addressing now the general case of floppy systems.