Experimental IR Spectra Research Articles

Synthesis, FT-IR, Bandgap Offset, Polarizability and Hyperpolarizability of 3,4-diamino-6-ehtyl-6H-pyrano[3,2-c]quinoline-2,5-dione (DAPQ) and Cu-2DAPQ as a Promising Organometallic Material: Experimental and Theoretical Studies

In our research, a comparative experimental and computational IR spectra of DAPQ have performed utilizing B3LYP/6-311G level. DAPQ hold over total dipole moment (TDM) (5.18 Debye), and HOMO/LUMO offset (3.76 eV). A theoretical model has been established to inspect the interaction between Cu+4 and N atoms associated with (-NH2)2 terminals of DAPQ. TDM for Cu-2DAPQ has been improved by 70.38% (17.49 Debye). Also, Cu-2DAPQ spin became doublet, which gives rise to the band splitting into Alpha and Beta MOs with energies 2.58 and 1.31 eV, respectively. Moreover, Cu-2DAPQ hyperpolarizability (βtot) is 200 times larger over urea (ref. βurea = 0.3728 x10-30 esu). Eventually, the non-linear optical response has been improved by 94.53%. Such outstanding improvement nominates Cu-2DAPQ as a promising MOF material for both Photovoltaic and non-linear optics applications.

Conductivity increase effect in nanocomposite polymer gel electrolytes: manifestation in the IR spectra

Nanocomposite polymer electrolytes based on poly(ethylene glycol) diacrylate and 1 M LiBF4 solution in γ-butyrolactone containing SiO2 nanoparticles were studied by FT IR spectroscopy. Quantum chemical modeling of five different solvate complexes of ions composed of LiBF4 with solvent molecules was carried out and their theoretical IR spectra were calculated. The compositions of the solvate complexes of LiBF4 in the nanocomposite gel electrolyte were studied by comparing the experimental and theoretical IR spectra. It was concluded that the conductivity peak observed upon adding 2 wt.% SiO2 is due to the appearance of mobile ions as a consequence of ionic dissociation on the surface of nanoparticles at their optimal configuration.

Surface Acidity Characterization of Metal-Doped Amorphous Silicates via Py-FTIR and 15N NMR Simulations

Metal-doped amorphous silicates are effective acidic catalysts for numerous industrial applications, including dehydration of alcohols, hydrodeoxygenation of biomass, and metathesis of olefins. The acidity of these catalysts is derived from the metal dopant and is experimentally characterized using a number of techniques, such as ammonia temperature-programmed desorption (NH3-TPD), pyridine Fourier transform infrared (Py-FTIR), and 15N nuclear magnetic resonance (NMR) spectroscopy of either probe molecule. Although these measurements provide information regarding the amount and strength of the acid sites, they alone do not provide any detail about the local structure around the metal center, which hampers the ability to systematically design better catalysts. In this study, we present density functional theory (DFT) simulations of Py-FTIR and 15N NMR spectra to characterize the local structure and acidity strength of metal-doped silicate clusters. We perform calculations on the model structures compiled in the METal-doped Amorphous SIlicate Library (METASIL), which aims at providing realistic amorphous structures for Zr-, Nb-, and W-doped silicates. By matching the calculated normal mode frequencies with experimental IR spectra, we reproduce the differentiation between Lewis and strong Brønsted acid sites. However, our simulations show that the coordination of Py to weak Brønsted acids is indistinguishable from that to metal sites, as they elicit similar frequency shifts. On the other hand, 15N NMR can distinguish between Py interacting with metal centers, weak and strong Brønsted acid sites, and it may be able to identify the structure of metal dopants. Therefore, these results can be used to provide theoretical support for the design of new catalytic materials.

Modelling IR Spectra of Sulfonated Polyether Ether Ketone (SPEEK) Membranes for Fuel Cells

SPEEK (sulfonated polyether ether ketone) membranes have been prepared and characterized. The SPEEK membrane geometry and theoretical vibration spectra calculated using density functional theory (DFT) as depending from membrane chain length and polymer cross-linking. Analyzed the limitations of the method by comparing theoretical and experimental IR spectra.

DFT zwitterion model for vibrational and electronic structure of unnatural 3-amino-3-(4-fluorophenyl)propionic acid, aided by IR and Raman spectroscopy

3-Amino-3-(4-fluorophenyl)propionic acid - a fluorinated building block in synthesis and a non-proteinogenic amino acid - belongs to the class of β-amino acids. We present here ab initio and DFT computed zwitterionic (ZW) monomer and dimer structures of 3-Amino-3-(4-fluorophenyl)propionic acid. These structures comprise intra- and inter-H-bonds (dimer), namely, N–H⋯O bonds formed between NH3+ and COO¯ moieties and the inter-N−H⋯O bond vibrational modes are correlated to the characteristic absorptions in the experimental IR spectrum. We propose two structures for 3-Amino-3-(4-fluorophenyl)propionic acid: a ZW monomer resulting from the explicit solvation model with four water molecules and a ZW dimer resulting from the implicit solvation model in water. By varying the bond length, rH … O around 1.70 Å, we get stable degenerate structures, getting the most stable ZW dimer mentioned above at 1.72 Å. Computed vibrational frequencies of NH3+ and COO¯ moieties for the ZW cluster and dimer complement each other in so far as good agreement with experimental IR and Raman spectra. We also have characterized both H-bonds using electronic properties computed from NBO, AIM and NCI methods. The natural bond analysis has shown that in both intra- and inter- N–H⋯O bonding, there is delocalization of electronic charge from n orbital on the O atom to σ∗ orbital on the N atom. The bond critical points are present between the cationic NH3+ and anionic COO¯ moieties along with atomic bond path confirming the N–H⋯O bond and is shown to be medium strong by NCI.

Synthesis and Characterization of the Tetrafluoridochlorates(III) A[ClF4] (A = K, Rb, Cs)

Single‐crystalline tetrafluoridochlorates(III) A[ClF4] (A = K, Rb, Cs) were synthesized from solvolysis reactions of alkali metal fluorides in liquid chlorine trifluoride. The structures were examined by means of single‐crystal X‐ray diffraction. K[ClF4] crystallizes in the K[BrF4] structure type, whereas the Rb and Cs compounds crystallize in the Li[AuF4] structure type. The compounds were further characterized by Raman and IR spectroscopy. Solid‐state quantum‐chemical calculations with hybrid density functional methods reproduced the experimental structures and enabled the interpretation of the experimental Raman and IR spectra.

Experimental and DFT Studies of Hybrid Silver/Cdots Nanoparticles.

In this work, the combination of experimental and theoretical results was employed to confirm an interaction between Cdots and AgNPs in the silver/Cdots hybrid nanoparticles. The experimental data obtained by UV-vis, IR, ζ potential, and TGA techniques were correlated and interpreted by calculations obtained by DFT. In particular, an interaction between the -COO- functional group of the Cdots with AgNPs was revealed. As consequence of this interaction, a frequency shift and a higher absorption intensity in the IR of the -OH group in the Cdots was theoretically predicted and also observed in the experimental IR spectra. Moreover, a bonding and charge distribution analysis was also carried out. These results constitute new physical insight for the Ag@Cdots system. Additionally, based in this type of interaction, energy calculations explained the negative charge surrounding the AgNPs, which was detected by ζ potential measurements. This systematic methodology not only is useful for this nanoparticles system but also could be used to analyze the interaction between the components that constitute other types of hybrid nanoparticles.

Theoretical and infrared spectroscopy study of the structure of copper(II) poly-5-vinyltetrazolate and the products of its thermolysis

The structure of copper(II) poly-5-vinyltetrazolate and the products of its thermolysis has been studied by means of density functional theory and infrared spectroscopy. Copper(II) poly-5-vinyltetrazolate has been obtained and subsequently subjected to thermolysis. Infrared spectra of copper(II) poly-5-vinyltetrazolate and the products of its thermolysis have been recorded. The possible ways of coordination of copper(II) ions with tetrazole-containing ligands were established by analyzing the calculated molecular electrostatic potential distribution and comparing the calculated IR-spectra of the model structures to the experimental ones. It has been shown that the best agreement between the calculated and experimental data is observed for the model with three-coordinated copper(II) ions, which includes both the tetrazole-containing ligands coordinating two copper(II) ions through N(1)- and N(3)-atoms of the tetrazole ring, and the tetrazolecontaining ligands coordinating one copper(II) ion through either the N(2)- or the N(3)-atom. Recently we have shown that the product of thermolysis of copper(II) poly-5-vinyltetrazolate exhibits high catalytic activity in homocoupling of phenylacetylene and Huisgen [3 + 2]-cycloaddition. To establish the structure of the products of thermolysis of copper(II) poly-5-vinyltetrazolate, seven possible products have been proposed based on the analysis of the structure of copper(II) poly-5-vinyltetrazolate and the experimental IR-spectrum. IR-spectra of all proposed products have been calculated and the results of the calculations have been compared with the experimental IR-spectrum of copper(II) poly-5-vinyltetrazolate thermolysis product. It has been shown that the main product of thermolysis is cis-polycyanoacetylene.

Vibrational Spectra of the Ruthenium–Tris-Bipyridine Dication and Its Reduced Form in Vacuo

Experimental IR spectra in the 500–1850 cm–1 fingerprint frequency range are presented for the isolated, gaseous redox pair ions [Ru(bpy)3]2+, and [Ru(bpy)3]+, where bpy = 2,2′-bipyridine. Spectra are obtained using the FELIX free-electron laser and a quadrupole ion trap mass spectrometer. The 2+ complex is generated by electrospray ionization and the charge-reduced radical cation is produced by gas-phase one-electron reduction in an ion–ion reaction with the fluoranthene radical anion. Experimental spectra are compared against computed spectra predicted by density functional theory (DFT) using different levels of theory. For the closed-shell [Ru(bpy)3]2+ ion, the match between experimental and computed IR spectra is very good; however, this is not the case for the charge-reduced [Ru(bpy)3]+ ion, which demands additional theoretical investigation. When using the hybrid B3LYP functional, we observe that better agreement with experiment is obtained upon reduction of the Hartree–Fock exact-exchange contribution from 20% to about 14%. Additionally, calculations using the M06 functional appear to be promising in terms of the prediction of IR spectra; however, it is unclear if the correct electronic structure is obtained. The M06 and B3LYP functionals indicate that the added electron in [Ru(bpy)3]+ is delocalized over the three bpy ligands, while the long-range corrected LC-BLYP and the CAM-B3LYP functionals show it to be more localized on a single bpy ligand. Although these latter levels of theory fail to reproduce the experimentally observed IR frequencies, one may argue that the unusually large bandwidths observed in the spectrum are due to the fluxional character of a complex with the added electron not symmetrically distributed over the ligands. The experimental IR spectra presented here can serve as benchmark for further theoretical investigations.

Correlation between the conformational crossover of carbamazepine and its polymorphic transition in supercritical CO2: On the way to polymorph control

In this paper we have established a correlation between the conformation crossover of carbamazepine and associated polymorph transformation. This was achieved by using a combination of quantum chemical calculations and in situ IR spectroscopy for performing a conformational analysis of carbamazepine molecules in its saturated solution in scCO2 being in permanent contact with the carbamazepine solid form. Using quantum calculations, we determined two carbamazepine conformers, whose spectral signatures were then found in experimental IR spectra. Further analysis of the IR spectra allowed us to quantify the distribution of these conformations in supercritical CO2. We found that this distribution can be changed by heating from 40°C to 110°C along two isochores at 1.1 and 1.3 of the critical CO2 density. Using in situ Raman spectroscopy we proved that the appearing conformational crossover correlates with the polymorphic transformation of the carbamazepine solid form. Moreover, this transformation was proved by the results of IR diffuse reflection spectroscopy.

Searching for correlations between vibrational spectral features and structural parameters of silicate glass network

AbstractInfrared (IR) and Raman spectroscopic features of silicate glasses are often interpreted based on the analogy with those of smaller molecules, molecular clusters, or crystalline counterparts; this study tests the accuracy and validity of these widely cited peak assignment schemes by comparing vibrational spectral features with bond parameters of the glass network created by molecular dynamics (MD) simulations. A series of sodium silicate glasses with compositions of [Na2O]x[Al2O3]2[SiO2]98−x with x = 7, 12, 17, and 22 were synthesized and analyzed with IR and Raman. A silica glass substrate and a crystalline quartz were also analyzed for comparison. Glass structures with the same compositions were generated with MD simulations using three types of potentials: fixed partial charge pairwise (Teter), partial diffuse charge potential (MGFF), and bond order‐based charge transfer potential (ReaxFF). The comparison of simulated and experimental IR spectra showed that, among these three potentials tested, ReaxFF reproduces the concentration dependence of spectral features closest to the experimentally observed trend. Thus, the bond length and angle distributions as well as Si–Qn species and ring size distributions of silica and sodium silicate glasses were obtained from ReaxFF‐MD simulations and further compared with the peak assignment or deconvolution schemes—which have been widely used since 1970s and 1980s—(a) correlation between the IR peak position in the Si–O stretch region (1050‐1120 cm−1) and the Si–O–Si bond angle; (b) deconvolution of the Raman bands in the Si–O stretch region with the Qn speciation; and (c) assignment of the Raman bands in the 420‐600 cm−1 region to the bending modes of (SiO)n rings with different sizes (typically, n = 3‐6). The comparisons showed that none of these widely used methods is congruent with the bond parameters or structures of silicate glass networks produced via ReaxFF‐MD simulations. This finding invokes that the adequacy of these spectral interpretation methods must be questioned. Alternative interpretations are proposed, which are to be tested independently in future studies.

Experimental and computational analysis of 1-(4-chloro-3-nitrophenyl)-3-(3,4-dichlorophenyl)thiourea

This manuscript presents the computational and experimental studies of a new thiourea derivative 1-(4-chloro-3-nitrophenyl)-3-(3,4-dichlorophenyl)thiourea (CNDCT). Scaled simulated and experimental IR and Raman spectra were compared and the vibrational modes are assigned to proper vibrations followed by potential energy distribution study. Weakening of N-H bond is observed from the red shift in NH stretching mode values from the theoretical wavenumber values. Natural bond orbital studies provide the stability of the molecule and predict the change properties upon the charge delocalization. Reactive sites in the molecule were identified using molecular electrostatic potential figures. According to QTAIM analysis, the locations of noncovalent interactions in CNDCT-1 and CNDCT-3 are practically the same. The difference in case of the CNDCT-2 is that noncovalent interaction is formed between atoms N7-H30, instead between atoms O20-C12. Average Local Ionization Energy (ALIE) and Fukui functions provide information about the exact atoms susceptible to various attacks. The tendency of the molecule to undergo air autoxidation was found from the bond dissociation energies (BDE) values and the interaction of the molecules with solvent system was analyzed using and radial distribution functions (RDF) obtained from molecular dynamics (MD) simulations. NLO studies indicate that the candidate molecule is a good NLO material compared to that of urea. Docking studies reveal that the title compound shows the inhibitory activity against Farnesoid X receptor.

5-Methyl-4-[3-(2-oxopyrrolidin-1-yl)propyl]-2,4-dihydro-3H-1,2,4-triazol-3-one: Synthesis, Characterization, and DFT Study

5-Methyl-4-(3-(2-oxopyrrolidin-1-yl)propyl)-2,4-dihydro-3H-1,2,4-triazol-3-one was synthesized and characterized by X-ray, FTIR and NMR spectroscopic techniques. The molecular geometry and spectral parameters of the title compound were also computed by the DFT/B3LYP76-311++G(d,p) method, and the theoretical data showed a good agreement with the experimental ones. The differences between the theoretical and experimental IR and NMR spectra supported the presence of inter- and intramolecular C-H⋯O and intermolecular N-H⋯O hydrogen bonds, which were revealed by X-ray analysis. Nonlinear optical (NLO) properties of the title compound were analyzed by the DFT/B3LYP/6-311++G(d,p) method by calculating the mean polarizability (α) and first-order hyperpolarizability values (β) (α = 22.0746454×10−24, β = 10.1110649×10−31 esu). As compared with the corresponding data for urea (α = 4.9067×10−24, β = 7.8782×10−31 esu), these values suggest promising NLO properties.

The interplay of VSCF/VCI calculations and matrix-isolation IR spectroscopy – Mid infrared spectrum of CH3CH2F and CD3CD2F

We present the first matrix-isolation infrared (MI-IR) spectra of CH3CH2F and its isotopologue CD3CD2F in Neon and Argon matrix, together with new gas-phase IR spectra. Extensive vibrational self-consistent field and configuration interaction (VSCF/VCI) calculations are performed, based on an ab initio potential energy surface at ae-CCSD(T)-F12a/cc-pCVTZ-F12 level of electronic structure theory. We encounter an excellent agreement between VCI calculated transitions and the experimental MI-IR and gas-phase IR spectra. Mean absolute deviations are scattering between 1 and 4 cm−1. The interplay of accurate vibrational structure calculations and high-resolution infrared experiments enables unprecedented insights in the CH respectively CD stretch region, providing the first rigorous assignment of the energetically very close ν1,ν12 and ν13 fundamental transitions.

Tailored synthesis of unsymmetrical tetradentate ONNO schiff base complexes of Fe(IIl), Co(II) and Ni(II): Spectroscopic characterization, DFT optimization, oxygen-binding study, antibacterial and anticorrosion activity

Abstract Two Schiff base ligands namely bis-2-((1E)-((Z)-2-(1,2-diphenylethylideneamino) phenylimino)methyl)phenol (L1) and bis-2-((1E)-((E)-2-(1-phenylethylideneamino)phenylimino) methyl)phenol (L2) were synthesized by tailored reaction of o-phenylenediamine with o-hydroxybenzaldehyde and 2-hydroxy-1,2-diphenylethanone/o-hydroxyacetophenone. The reaction of these ligands with Fe(III), Co(II), and Ni(II) salts yielded six complexes. Ligands and their metal derivatives have been characterized by elemental analysis, molar conductance, magnetic susceptibility, FT-IR, UV–Vis, ESI-mass, 1H NMR, 13C NMR and EPR analysis. Using Gaussian 09 molecular modelling, bond lengths, bond angles and Mulliken charge were also evaluated. In addition to this study of HOMO and LUMO molecular orbital have been performed. The FT-IR spectra have suggested that ligand is coordinated with metal through azomethine-N and phenolic-O. Experimental and theoretical IR and NMR spectrum of ligand L1 and complex 2 exhibits quite good correlation. ESR spectrum of complex 2 at LNT suggests octahedral geometry around Co(II). Complexes were studied for their oxygen-binding activity and displayed significant oxygenation reaction. The thermodynamic parameters such were also calculated. The compounds were screened for antibacterial activity against gram-negative bacteria Escherichia coli and compared with Amoxicillin. Complexes have exhibited significant antibacterial activity. The corrosion inhibition effect of ligands and complexes on mild steel in acidic medium was studied for 24, 48 and 72 h using weight loss measurement.

X-ray and vibrational analysis of amino and chloro bibenzyl 4,4′-derivatives supported by quantum chemical calculations

Abstract Two derivatives of bibenzyl, 4,4′-diaminobibenzyl and 4,4′-dichlorobibenzyl, were studied for the first time by X-ray diffraction and vibrational spectroscopy in this work. The vibrational assignment was made in detail using Raman and IR measurements accompanied by DFT simulations performed in hybrid B3LYP version employing 6-31G (d,p) basis set. The normal modes interpretation was carried out on the basis of a potential energy distribution obtained by VEDA program. The structural diversity, consisting in the existence of eight crystallographically independent structures, is observed for DCBB while only one structure was revealed in crystal of DABB. This difference is attributed to the stabilization effect provided by intermolecular interactions between the amino groups and water molecules included in the crystalline structure of DABB. Trustworthy shortening of C (sp3)-C (sp3) bond length in ethane fragment was established in the crystal structures of both compounds and is explained by torsional vibration of C—Ph bonds. The characteristic vibrational modes of ethane fragment were assigned in the experimental Raman and IR spectra. The vibrations with participation of functional groups were also distinguished in the measured spectra. The obtained new data about bibenzyl derivatives could contribute in a better understanding of physical chemistry of compounds with freedom of rotation around the central C–C bond that is significant for targeted development of nanomachines and other prospective molecular systems.

Spectroscopically Resolved Binding Sites for the Adsorption of Sarin Gas in a Metal-Organic Framework: Insights beyond Lewis Acidity.

Here we report molecular level details regarding the adsorption of sarin (GB) gas in a prototypical zirconium-based metal-organic framework (MOF, UiO-66). By combining predictive modeling and experimental spectroscopic techniques, we unambiguously identify several unique bindings sites within the MOF, using the P═O stretch frequency of GB as a probe. Remarkable agreement between predicted and experimental IR spectrum is demonstrated. As previously hypothesized, the undercoordinated Lewis acid metal site is the most favorable binding site. Yet multiple sites participate in the adsorption process; specifically, the Zr-chelated hydroxyl groups form hydrogen bonds with the GB molecule, and GB weakly interacts with fully coordinated metals. Importantly, this work highlights that subtle orientational effects of bound GB are observable via shifts in characteristic vibrational modes; this finding has large implications for degradation rates and opens a new route for future materials design.

Jahn-Teller effect versus spin-orbit coupling: The structure of the free molybdenum pentafluoride molecule

The complete active space self-consistent field (CASSCF) and multiconfigurational quasi-degenerate second-order perturbation (MCQDPT2) calculations have been used to study the ground and low-lying excited electronic states of MoF5. Scalar-relativistic effects and spin-orbit coupling (SOC) have been taken into account employing the third-order Douglas-Kroll-Hess (DKH) Hamiltonian and full Breit-Pauli operator, respectively. The optimization and the calculation of the Hessian matrix have been performed by non-routine procedure employing the symmetry coordinates for all considered (D3h, C2v and C4v) geometrical configurations. The trigonal bipyramidal D3h structure of molybdenum pentafluoride MoF5 possesses two-fold degenerate ground first excited electronic orbital state and undergoes Jahn-Teller distortion to the C2v configurations. Accounting of SOC quenches the JT effect. As a result the D3h structure of MoF5 is no longer the conical intersection of two adiabatic potential energy surfaces (APES) but two separated APES corresponding to ground (12E1/2) and nearest excited (12E3/2) spin-orbit states are appeared instead. The D3h trigonal bipyramidal structure in the ground spin-orbit state corresponds to the 2-nd order saddle point on APES and lies above the minima (C2v structure, 12E1/2 state) by 244 cm−1. The warping barrier (another C2v structure) in the trough of APES and the Berry pseudorotation barrier (C4v structure, ground spin-orbit state 2E3/2) are 19 and 310 cm−1, respectively. Therefore MoF5 molecule is characterized in the gas phase by a large-amplitude motion of fluorine atoms in the equatorial plane and non-rigid intramolecular rearrangement by Berry mechanism. Despite such non-rigid nuclei dynamic, the calculated harmonic frequencies of MoF5 molecule do not contradict to available experimental IR spectrum. The repeat refinement of MoF5 gas electron diffraction data has been carried out using static and pseudoconformer models based on the SO-MCQDPT2 results. Corresponding to only extreme points on APES the configurations have been included into the pseudoconformer model. The both models have been fitted to the experimental data by the same quality.

Synthesis, crystal structure, and properties of new compounds [NH4]4[SbF4]2[NbOF5], K4[SbF4]2[NbOF5], and [NH4]4[SbF4]2[SnF6

Three new isostructural complex compounds – [NH4]4[SbF4]2[NbOF5] (1), K4[SbF4]2[NbOF5] (2), and [NH4]4[SbF4]2[SnF6] (3) – have been synthesized, and their structures have been determined. The compounds have appeared to crystallize in a triclinic system, the spatial group P1¯. The structures of the compounds are built from anion layers of the composition [Sb2NbOF13]4–∞2 in 1, 2 and [Sb2SnF14]4–∞2 in 3. The anion layers alternate with the layers of potassium cations in 2 and with ammonium cations in 1, 3. The anion layers of [Sb2NbOF13]4–∞2 in 1, 2 and [Sb2SnF14]4–∞2 in 3 are formed by edge- and corner-sharing centrosymmetric Sb2F12 dimer groups and NbOF5 (for the 1 and 2) and SnF6 (for 3) distorted octahedra. The melting points of the compounds 1-3 along with K4[SbF4]2[SnF6] (4) have been determined: 454 K – for 1, 556 K – for 2, 463 K – for 3, 559 K – for 4. Based on quantum-chemical calculations of vibrational frequencies, the assignment of bands in the experimental IR and Raman spectra of the synthesized compounds have been performed.

Theoretical (DFT) and experimental (Raman and FTIR) spectroscopic study on communic acids, main components of fossil resins.

The objective of this work is to establish a spectral assignment of several communic acids. The most significant vibrational modes of three stereoisomers of communic acids [trans-, cis-, and iso- (or mirceo-)] are presented. They are showed throughout experimental Raman and IR spectra, and on the basis on calculations with Density Functional Theory (DFT) and the assignment of the spectral bands of different resins found in the literature. These three communic acids studied are the most important isomers present in the scaffold of the fossil resins Class I, as monomers or co-polymerized according to several authors. These kinds of terpenes are used as starting material, for example, for the synthesis of the fungicide and compounds bioactives. In a novel way, it is reported jointly the assignment of the experimental Infrared and Raman modes together with theoretical modes, since normally the authors tend to focus on one or another spectroscopic technique only. These results can be used as a reference for distinguishing amber from less matured resins as copal, determining the local origin of archaeological fossilized resins. Moreover, they will serve as help to differentiate between real and imitation ambers.