C2v Symmetry Research Articles

The Au12 Gold Cluster: Preference for a Non-Planar Structure

The transition point from a two-dimensional (2D) to a three-dimensional (3D) structure in a series of small gold clusters remains a topic of continuing debate. In the present study, coupled-cluster CCSD(T) and DFT calculations are performed to re-examine the relative energies of several low-lying isomers of Au12, aiming to shed new light on this issue. At odds with many previous reports on the preference of a planar di-capped elongated-hexagon structure, the Au12 size is found to energetically prefer a globular cup-like form with C2v symmetry. While DFT results are not able to assign the most stable form of Au12 as the relative energies between the lowest-lying isomers are strongly functional-dependent, coupled-cluster theory calculations point out the preference of a 3D structure for having a D3h symmetry. Such a prediction is further supported by a comparison of the vibrational spectra computed using the revTPSS density functional with the available experimental infrared ones that were previously recorded from the far-IR multiple photon dissociation (FIR-MPD) experiment.

Polarization-independent tetramer metasurface with multi-Fano resonances based on symmetry-protected bound states in the continuum

The bound state in the continuum (BIC) has drawn much attention in electromagnetics due to its infinite lifetime and quality factor. By the method of breaking the symmetry in the metasurface, the optically invisible BIC can be converted into visible quasi-BIC with ultra-high quality factor. However, symmetry-breaking metasurfaces often suffer from polarization sensitivity due to structural or field asymmetry. In this paper, we propose a metasurface consisting of nanodisk tetramer clusters to realize the transformation from BICs to quasi-BICs and support four resonances in the near-infrared range. The in-plane center square defect is introduced to provide symmetry-breaking while C4v symmetry is maintained. By performing the multipole decomposition and near-field analysis, these four modes can be demonstrated to be excited by electric quadrupole (EQ), magnetic quadrupole (MQ), magnetic dipole (MD) and toroidal dipole (TD) moments. We demonstrate the full angles polarization-independent characteristic of the metasurface and investigate the robustness by introducing off-center square defects. In addition, we also evaluate the sensing performance of the metasurface as a refractive index sensor. We believe that this work could provide new references for the polarization insensitive metasurface with multiple resonances and help to develop the applications such as biochemical sensing, low-threshold lasing and nonlinear devices.

183W Nuclear Magnetic Resonance and Photocatalysis Studies of Two Ruthenium-Decorated Isopolyoxometalates {Ru2W10} and {Ru2W13} via pH-Induced Assemblies.

Two structurally intriguing Ru-containing isopolyoxometalates [(Ru(OH))2O(W5O18)2]8- (1) and [(W5O18)(Ru2W8O31)]12- (2) were constructed from subtly different conditions. Single-crystal X-ray diffraction indicated that the precise pH modification has allowed us to trap a diruthenium-oxo core within different isopolyoxotungstate species. Compound 1 is the first sandwich-type ruthenium isopolyoxotungstate consisting of a linear {(HO)Ru-O-Ru(OH)} unit and two Lindqvist-type {W5} building blocks, while a ligand replacement of {W5} with an unusual {W8} ring in the case of compound 1 produced a unique embedded-type compound 2 with a quasi-linear {Ru-O-Ru} core. In addition to being determined in the solid state, crystal structures of 1 and 2 were also confirmed by 183W nuclear magnetic resonance (NMR) spectroscopy and electrospray ionization-mass spectrometry (ESI-MS) in solution. 183W NMR spectrum demonstrated that the two-line pattern of 1 (with approximately 4:1 relative intensities) is consistent with the pseudo-D2h symmetry observed in the solid state. However, two other lines were observed in 2 according to the C2v symmetry but not in accord with the expected 4/4/4/1 ratio in the crystalline state, which indicated that the structure of 2 could not be maintained completely in aqueous solution. After recrystallizing the solid sample of 2 in water, the crystal structure of 2 partly converted to the structure of 1, and the transformation was determined by the combined results of 183W NMR, ESI-MS and single-crystal X-ray diffraction measurements. Catalytic investigations showed that their sodium salts presented excellent photocatalytic activities toward the benzylamine oxidation reaction induced by visible light (λ > 400 nm). The structures of the two compounds can still be maintained without a significant yield decrease after five continuous reaction cycles. Furthermore, both catalysts 1 and 2 could proceed with the oxidative coupling reaction smoothly for most of the primary benzylamine derivatives bearing various functional groups (H, F, Cl, Br, and Me) in good to excellent yields.

Can Something that is Called “Sub” be Superb? The Case of Subphthalocyanines

Subphthalocyanines (SubPcs) are well-known cone-shaped chromophores consisting on three 1,3-diiminoisoindole units assembled around a boron atom. As a result of their 14 pi-electron aromatic core and their tetrahedral geometry, SubPcs exhibit outstanding physical and optoelectronic properties (e.g., strong dipole moment, excellent light absorption in the 550-650 nm, rich redox features, and excellent charge transport capabilities), that have been skilfully used in variety of applied fields, such as molecular photovoltaics, among others. SubPcs were used by us as non-fullerene acceptors in bulk heterojunctions (BHJ) solar cells. On the other hand as part of our systematic investigation in the preparation and study of novel SubPc-based D–A systems, we have used 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) as partner for SubPcs. Moreover, in the case of unsymmetrically substituted SubPcs (i.e., prepared by cyclotrimerization of a phthalonitrile with no C2v symmetry), they present inherent chirality and the corresponding couple of enantiomers can be isolated Columnar aggregates based on chiral SubPcs have been also prepared, giving rise to ferroelectric self-assembled molecular materials showing both rectifying and switchable conductivity. These chromophores have been incorporated in multicomponent systems showing a panchromatic response and allowing the tuning and controlling intramolecular FÖRSTER Resonance Energy Transfer for Singlet Fission.

Local strain-dependent Zeeman splitting in GaN:Eu

The electronic spins of rare-earth materials are attractive candidates for spin qubits and quantum memories. To access individual spins, tuning of the g-factor is desirable. Here, we report on local strain-dependent g-factors of the 5D0–7F2 transitions of Eu3+ centers in GaN:Eu thin films. We have found a clear correlation between the effective g-factor and the emission energy shift induced by the local strain. The combination of micro-photoluminescence and scanning electron microscope/electron backscattering diffraction measurements has revealed that the compressive strain of 0.2%–0.4%, relative to a surrounding reference point, induces an energy shift of about 3 meV. The strain decreases the g-factor of the emission at 1.991 eV from 2.5 to 1.5, while the strain increases the g-factor of the emission at 1.994 eV from 1.1 to 1.7. The result suggests that the g-factor can be tuned by the local strain. On the basis of the strain-induced energy shift and the g-factor, we have identified the optical sites. The 5D0–7F2 transitions observed in this study consist of three optical sites with C3v symmetry and one site with C1h symmetry.

Formula omitted]-type doubling in the rotational spectrum of CH[formula omitted]–He: A group theoretical explanation

In a previous paper, we reported the pure rotational spectrum of the CH3+–He ion observed in a 22-pole ion trap by IR-MW double resonance spectroscopy [Töpfer et al. (2018)]. In that work the K=1 rotational levels in the ground state of the ion were observed to be split, i.e. the K-type doubling was observed. This finding would be consistent with a slightly asymmetric rotor of Cs symmetry, although ab-initio calculations predict that the equilibrium structure of the ion is of C3v symmetry. In the present study we inspect the energy-level correlation-diagram between the semi-rigid symmetric-top (C3v), the free internal-rotor (C3v(M)), and the semi-rigid asymmetric-top models (Cs), by using group theory, especially the correlation and reverse correlation in the symmetry representations. We find that the lowest K=1 rotational levels of the CH3+–He ion can be of A1⊕A2 symmetry rather than of E symmetry, and thus they can be split depending on the nature of the C–He bending vibration.

Toroidal Dipole Excitation in Metamaterial Perfect Absorber Consisting of Dielectric Nanodisks Quadrumer Clusters and Spacer on Metal Substrate

We proposed an infrared narrowband metamaterial perfect absorber (MPA) which is induced by toroidal dipole resonance in a dielectric-metal hybrid system. The MPA is composed of amorphous-silicon (a-Si) nanodisk quadrumer clusters, dielectric spacer, and Au substrate, where the dielectric spacer is inserted between Si disk quadrumer and Au substrate. Near field distribution and multipole decomposition of far-field, scattering powers show that toroidal dipole mode is formed by opposite phase magnetic dipoles in neighboring Si nanodisks. The effects of geometric and material parameters on absorption characteristics were explored. The sensing performance of the MPA was also evaluated. The proposed MPA has potential applications in air sensing applications. Since the nanodisks quadrumer of the MPA retains C4v symmetry, perfect absorption band is polarization independent. Furthermore, the absorption quality factor of the hybrid dielectric-metal hybrid absorber is higher than that of all-metal perfect absorbers, thanks to the low loss feature of the dielectric resonator.

Preparation of highly branched polyolefins by controlled chain‐walking olefin polymerization

AbstractA series of α‐diimine nickel(II) catalysts bearing different para‐substituted groups, {[(4‐R‐2,6‐Me2‐C6H2NC)2Nap]NiBr2, Nap: 1,8‐naphthdiyl; R = CHMePh (C1); R = CHPh2 (C2); R = tBu (C3); R = Br (C4); R = Me (C5)}, were synthesized and characterized. The molecular structures of C1 and C3 were determined by single crystal X‐ray analysis and show distorted tetrahedron geometry with C2v symmetry. The catalytic behaviors of these catalysts toward ethylene polymerization were investigated in the presence of diethylaluminum chloride (Et2AlCl) as a cocatalyst. The fast chain‐walking process in N,N‐chelated nickel system can be efficiently modulated via the introduction of para‐sec‐phenethyl substituents with improved thermal stability and catalytic performance. C1‐Et2AlCl exhibited high thermal stabilities and high activities reaching 4.61 × 106 g PE (mol Ni h)−1, producing highly branched amorphous polyethylenes (up to 143 branches/1000C) with high molecular weight and narrow polydispersity. This catalyst system conducted successfully conducted 2‐octene polymerization in comparison with the corresponding 1‐octene polymerization. The result demonstrated 2‐octene polymerized slower than 1‐octene and produced the highly‐branched poly(2‐octene)s with approximately 120 branches/1000C, including methyl, ethyl, amyl, and hexyl branches and a small amount of the long methylene sequence due to monomer isomerization.

Toward Detection of FeH+ in the Interstellar Medium: Infrared Multiple Photon Dissociation Spectroscopy of Ar2FeH.

The iron hydride molecular cation FeH+ is expected to be present in the interstellar medium. Because of the lack of laboratory data, it is yet to be identified in spectrally resolved astronomic observations. As a benchmark for computational predictions and to guide an experimental search for the ro-vibrational lines of FeH+, we performed infrared multiple photon dissociation (IRMPD) spectroscopy of FeH+ tagged with two argon atoms. The Fe–H stretching mode in Ar2FeH+ is observed at 1860 cm–1. Combination bands of the Fe–H stretch with the two Fe–H bending and the asymmetric Fe–Ar stretching modes are observed at 2012 cm–1, 2054 cm–1, and 2078 cm–1. Quantum chemical calculations show that the molecule has C2v symmetry. The Ar–Fe–Ar bending mode at 46 cm–1 is significantly populated at the temperature of the experiment, causing thermal broadening of the Fe–H stretch and its redshift with increasing internal energy.

Raman Spectroscopic Studies on Aqueous Sodium Formate Solutions and DFT Calculations

NaHCOO(aq) and NaDCOO(aq) solutions were measured using Raman spectroscopy from dilute to concentrated solutions at 23 °C in water and heavy water from 50 to 4300 cm−1. A concentrated NaHCOO solution in heavy water was also measured. The Raman band parameters of HCOO−(aq) and DCOO−(aq) such as peak position, full width at half maximum (fwhm), integrated intensities, and depolarization values were determined. From the Raman spectroscopic data, it was concluded that the HCOO−(aq) and DCOO−(aq) symmetry is lower than C2v and probably as low as C1. In contrast to the solution state, tt normalsize tt normalsize {text{HCO}}_{2}^{ - } (tt normalsizettnormalsize {text{DCO}}_{2}^{ - }) possess C2v symmetry in the gas phase and the DFT frequencies are given. DFT frequencies on a cluster of HCOO−/DCOO− with five implicit water molecules in the first sphere and placed in a polarizable continuum deviate not more than 1–2% from the measured ones. In the Raman spectrum in NaHCOO(aq), a band doublet at 2730 cm−1 and 2820 cm−1 occurs instead of a single band. The band doublet is due to Fermi resonance and results from the interaction of the overtone of the bending C–H mode, 2ν6 at 1382 cm−1 and ν1. The undisturbed C–H stretching mode, ν1 amounts to 2785 cm−1. In DCOO−(aq), a Fermi doublet was also observed at 2030.5 and 2116.5 cm−1, and the undisturbed wavenumber position amounts to 2101 cm−1. Furthermore, a solution of HCOO− in D2O showed slightly changed frequencies compared with the ones in water caused by the solvent isotope effect. Ion pairing between Na+ and HCOO− characterizes the Raman spectrum at high solute concentrations which are melt-like enabling direct contact between the ions. A NaHCOO solution with high amounts of LiCl added showed large perturbations of the HCOO− bands especially νsCOO− and δ COO− of HCOO−and revealed a stronger affinity of Li+ toward HCOO−. The ion pairs formed are most likely contact ion pairs between Li+ and HCOO− which have different stoichiometry of Li+: HCOO− such as 1:1 and 2:1.Graphical

Preparation and characterization of antimony nanoparticles for hydrogen evolution activities

Modern research focuses exclusively on the search for relatively inexpensive, highly efficient electrocatalytic materials for the electrocatalytic hydrogen production water splitting reactions. Antimony is a chemical element having four allotropes with three oxidation states. Antimony is a semi-metal with elemental antimony. Recently, elemental antimony (Sb) with an extensive light absorption was recognized as good electrocatalytic for hydrogen evolution reactions. This study focuses on preparation and characterization of antimony nanoparticles for hydrogen evolution activities as explored. We report the structural, optical, vibrational, electrochemical properties of the pristine antimony nanoparticles for efficient catalytic material for electrochemical water splitting applications. The prepared antimony nanoparticles revealed the rhombohedral crystal structure formation with D3d5 (R 3¯ m) space group situated on symmetry C3v sites. In Raman studies, the peak appeared at 110.67 cm−1 corresponds to in-plane longitudinal vibration (Eg) and at 147 cm−1 for out of plane vibration (A1g) for pure antimony. The synergic effect of NMP and ultrasonication yields highly homogeneous antimony nanoparticles as evidenced from morphological analysis. From electrochemical impedance analysis, the solution resistance value of Sb-NMP is 1.67 Ω, which was small in comparison to the pure Sb (1.96 Ω) and Sb-Ball (1.93 Ω) and exhibited the good conductive nature of Sb-NMP nanomaterials. From electrochemical HER analysis, we found that the Sb-NMP showed the low 246 mV@10 mA/cm2 overpotential with low 186 mV/dec Tafel slope value. Furthermore, the chronoamperometry study exposed that the electrocatalyst Sb-NMP delivered an exceptional HER performance with high stability of 80% retention for continuous three hours measurements. Therefore, this study may perhaps facilitate the growth of antimony nanoparticles which can be used as an HER catalysts for improving the electrocatalytic HER activity.

Tuning symmetry-protected quasi bound state in the continuum using terahertz meta-atoms of rotational and reflectional symmetry.

Conventionally, a symmetry-protected quasi bound state of the continuum (BIC) becomes achievable by breaking the C2 symmetry of meta-atoms. Our work exhibits a novel approach to achieving dual band quasi-BIC by breaking the C2v symmetry into Cs symmetry. Also, we show that a single band quasi-BIC can be achieved by breaking the C2v symmetry into C2 symmetry. Our metasurface of C2v symmetry is composed of double gaps split ring resonator (DSRR), and it degrades to C2 symmetry when the double gaps are displaced in opposite directions. One band quasi-BIC can be observed occurring at around 0.36 and 0.61 THz respectively with the metasurface excited by x- and y-polarized terahertz radiation, respectively. A couple of dark dipole oscillator dominates the quasi-BIC at 0.36 THz, while a quadruple-like oscillator dominates the quasi-BIC at 0.61 THz. The damping ratio and coupling coefficients of the above single quasi-BIC are close to the orthogonal polarization of the incident terahertz wave. However, the metasurface of the DSRR array degrades down to Cs symmetry when the double gaps are displaced in the same directions. A dual band quasi-BIC (0.23 THz and 0.62 THz) is found to be sensitive to the y-polarized terahertz radiation. It is found that the inductive-capacitive (LC) resonance results in quasi-BIC at 0.23 THz, while a quadrupole-like oscillation results in quasi-BIC at 0.62 THz. The quasi-BIC at 0.62 THz has a higher coupling coefficient and lower damping ratio than quasi-BIC at 0.23 THz in a metasurface of Cs symmetry. The realization of the above locally symmetric breaking on the quasi-BIC of terahertz metasurfaces is helpful for the innovation of multi-band terahertz biosensors.

Keeping dysprosium in line: Trinuclear heterometallic MII2DyIII complexes with M=Cd, Co and Cu

AbstractFour new heterometallic trinuclear essentially linear (“in‐line”) MII2DyIII complexes (M=CdII (1), CoII (2), CuII (3, 4) were synthesised using the ligand 3,5‐di‐tert‐butylbenzoic acid (dtbbaH) in a MeCN : iPrOH (1–3) or in a MeOH : iPrOH : DMF (4) mixture. Single crystal structure analyses revealed the formation of [Cd2Dy(dtbba)6(iPrOH)2(H2O)2NO3] ⋅ iPrOH (1), [Co2Dy(dtbba)6(iPrOH)2(H2O)2NO3] ⋅ iPrOH (2), [Cu2Dy(dtbba)6(MeCN)4NO3] ⋅ MeCN (3) and [Cu2Dy(dtbba)6(iPrOH)1.68(DMF)1.32(H2O)NO3] ⋅ 3iPrOH ⋅ H2O (4). The M−Dy−M angles become more acute from (1) to (3) leading to decreased M⋅⋅M distances. The DyIII ions are 8‐coordinate with a distorted triangular dodecahedron geometry and a D2d symmetry whereas the geometry of the 5‐coordinate terminal MII ions can best be described as either distorted vacant octahedra or as spherical square pyramids with a C4v symmetry. Magnetic susceptibility measurements were performed on (1), (2) and (3) which allows a comparison of the effect of replacing highly anisotropic CoII with the quantum spin of CuII. Both (2) and (3) show effects of ferromagnetic interactions at low temperatures.

C–H⋯S Hydrogen Bond Assisted Supramolecular Encapsulation of Fullerenes with Nanobelts

C–H⋯S Hydrogen Bond Assisted Supramolecular Encapsulation of Fullerenes with Nanobelts

Paradimorphite, β-As4S3, a vintage new mineral from Solfatara di Pozzuoli and Vesuvius, Napoli, Italy

AbstractThe new mineral paradimorphite corresponds to the high temperature polymorph of As4S3, whose existence was supposed by Arcangelo Scacchi in 1850 in the fumaroles at the Solfatara di Pozzuoli, Campi Flegrei, near Napoli, Italy.Crystals of paradimorphite are orange yellow, transparent or semitransparent, with adamantine lustre. Habit is prismatic and observed forms are {110}, {101}, {111}, {100}, {010} and {001}. Tenacity is brittle, no distinct cleavage is observed and fracture is conchoidal. The mineral does not fluoresce in long- or shortwave ultraviolet light. No twinning is apparent. The streak is saffron yellow. Hardness (Mohs) = 1–2. The observed density is 3.510(3) g/cm3, calculated density is 3.500 g/cm3. The mineral is orthorhombic, space group Pnma, with a = 9.1577(7), b = 8.0332(6), c = 10.2005(8) Å, V = 750.41(10) Å3 and Z = 4. The eight strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 6.299(48)(011), 5.186(100)(111), 4.174(31)(201), 3.133(34)(022), 3.116(58)(212), 2.980(41)(122), 1.846 (27)(413) and 1.808(23)(134). The structure was refined to R = 0.0229 for 979 reflections with I >2σ(I). Crystals of paradimorphite contain As4S3 molecules, of idealised C3v symmetry, with the four arsenic atoms in a triangular pyramidal arrangement, with sulfur atom bridges on the three adjacent apical edges. Molecular dimensions and conformation are identical within standard uncertainties with those of the low-temperature polymorph dimorphite. No substantial differences, neither in the molecular packing nor in the molecular orientation, could be observed; minor differences being related to intermolecular distances only.

Torsional motions of the free and H-bonded hydroxyl groups of the catechol molecule

Torsional vibrations of free and hydrogen-bonded hydroxyl groups of the 1,2-dihydroxybenzene molecule are analyzed within the harmonic and anharmonic approximations, as well as by constructing a 2D potential energy surface formed by varying the torsional coordinates of the two OH groups. Calculation of the vibrational spectrum of the molecule in the harmonic and anharmonic approximations was performed at the MP2/acc-pVTZ level of theory. Calculations of the 2D potential energy surface were performed at the MP2/acc-pVTZ, MP2/CBS(T,Q), and CCSD(T)/acc-pVDZ levels of theory. Calculations of the 2D surfaces of dipole moment components and kinetic coefficients were performed at the MP2/cc-pVTZ and MP2/acc-pVTZ levels of theory. In the latter case, the formalism of Wilson’s s→ vectors was used. The energies of the first 100 stationary torsional levels are calculated and classified by irreducible representations of the molecular symmetry group C2V(M). Furthermore, the analysis of wave functions allowed us to assign most of the torsional states to the fundamentals, combinations, and overtones of the torsional vibrations of the hydroxyl groups of two conformers that have the point symmetry groups CS (I) and C2V (II). The tunneling frequencies between equivalent configurations of conformer I in the ground and excited torsional states are estimated. The calculated values of the frequencies of fundamental torsional vibrations of two OH groups and the tunneling splitting value of the first excited torsional state of the free hydroxyl group of conformer I are compared with the experimental data presented in a recently published work [J. Bruckhuisen et al., Molecules 26 (2021) 3645]. Torsional IR spectra of the molecule are modeled at different temperatures.

Topological Refraction in Kagome Split-Ring Photonic Insulators.

A valley-Hall-like photonic insulator based on Kagome split-ring is proposed. Theoretical analysis and numerical calculations illustrate that symmetry can be broken not only by global rotation but also individual rotation of the split rings, providing topological phase transitions. Furthermore, refraction of the edge state from the interface into the background space at Zigzag termination is explored. It is shown that positive/negative refraction of the outgoing beam depends on the type of valley (K or ), from which the edge state is projected. These results provide a new way to manipulate terahertz wave propagation and facilitate the potential applications in directional collimation, beam splitting, negative refraction image, etc.

Influence of ZnF2 and ZnCl2 on luminescence investigations and crystal field calculation of Eu3+ doped zinc oxide-phosphate glasses

A series of Eu3+-doped 70NaPO3–20ZnO-10(ZnF2/ZnCl2) glasses were prepared by conventional melting quenching method. The samples were characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), electron probe microanalysis (EDS/WDS) and optical spectroscopy. Using the emission spectra a set of Judd-Ofelt (JO) intensity parameters (Ω2, Ω4, Ω6) was refined, which in turn permitted to calculate transition probabilities (AED, AMD), branching ratios (β), radiative lifetimes (τrad) and stimulated emission cross-sections for the 5D0-7FJ transitions. The relative luminescence intensity ratio of 5D0-7F2-5D0-7F1 transitions has been evaluated to estimate the local site symmetry around the Eu3+ ions. Second and fourth rank crystal-field (CF) parameters together with the CF strength parameter have been reported for the first time for such study by assuming the C2v symmetry for the Eu3+ ions in both the phosphate glasses. Large stimulated emission cross-section, high branching ratios and quantum efficiencies (∼80%), also, intense red luminescence at 616 nm confirm that these present glasses suggesting for visible red lasers materials and optical devices.

Optical and photophysical properties of platinum benzoporphyrins with C2v and D2h symmetry

Platinum(II) mono- and di-benzoporphyrins carrying either ester or imide peripheral groups have been successfully synthesized. These benzoporphyrins possessing C[Formula: see text] and D[Formula: see text] symmetry were investigated using a range of techniques including UV-Vis and phosphorescence spectroscopy, differential pulse voltammetry, and transient absorption spectroscopy covering wide spatial and temporal ranges. Up to three oxidation and three reductions within the accessible potential window of dichlorobenzene were observed. Facile reductions for both mono- and dibenzoporphyrin derivatives, more so with imide peripheral substituents were witnessed. Computational studies were supportive of push-pull type interactions within these molecular systems. The formation of triplet excited states within 5 ps after laser excitation was confirmed by femtosecond transient absorption studies. Nanosecond transient absorption studies coupled with phosphorescence lifetime studies revealed relatively rapid relaxation of the triplet excited states as compared to a controlled platinum porphyrin suggesting push-pull type interactions on a slower time scale.

IR spectra of [formula omitted] in Ar and [formula omitted] cryomatrices: Evidence of unusual band splitting in [formula omitted] matrix

Matrix isolation IR spectra of CH2I2 in N2 matrix are analysed using IR spectra obtained in the Ar matrix, quantum chemical calculations, and molecular point group symmetry to determine the origin of the unusual splitting observed in the CH2 antisymmetric stretching (ν6), CH2 rocking (ν7), CH2 wagging (ν8), and CI2 antisymmetric stretching (ν9) modes of CH2I2 only in N2 matrix and not in Ar matrix. The ν6, ν7, ν8, and ν9 vibrational modes belong to either B1 or B2 irreducible representations under C2V point group symmetry. IR spectra in N2 matrix is reported for the first time. IR spectra recorded in Ar matrix are consistent with previous reports. Electronic structure calculations have been performed to obtain simulated IR spectra of CH2I2 with C2V and C2 point group symmetries, (CH2I2)2 conformers, [CH2I2-H2O], and [CH2I2-(N2)4]. IR spectra obtained in Ar and N2 matrices originate from CH2I2, (CH2I2)2, and splitting of IR peaks in N2 matrix. Splitting of the IR peaks of CH2I2 in solid state is described by Davydov splitting or factor group splitting. The observed splitting of IR peaks in N2 matrix is due to the lowering of symmetry of CH2I2 from C2V to one of its sub groups due to the perturbation of the rigid N2 matrix that possess quadrupole moment.