Chemical Reactivity Indices Research Articles

Designing of Thiophene [3, 2-b] Pyrrole Ring-Based NFAs for High-Performance Electron Transport Materials: A DFT Study.

Among the blended components of a photoactive layer in organic photovoltaic (OPV) cells, the acceptor is of high importance. This importance is attributed to its increased ability to withdraw electrons toward itself for their effective transport toward the respective electrode. In this research work, seven new non-fullerene acceptors were designed for their possible utilization in the OPVs. These molecules were designed through side-chain engineering of the PTBTP-4F molecule, with its fused pyrrole ring-based donor core and different strongly electron-withdrawing acceptors. To elucidate their effectiveness, the band gaps, absorption characteristics, chemical reactivity indices, and photovoltaic parameters of all of the architecture molecules were compared with the reference. Through various computational software, transition density matrices, graphs of absorption, and density of states were also plotted for these molecules. From some chemical reactivity indices and electron mobility values, it was proposed that our newly designed molecules could be better electron-transporting materials than the reference. Among all, TP1, due to its most stabilized frontier molecular orbitals, lowest band gap and excitation energies, highest absorption maxima in both the solvent and gas medium, least hardness, highest ionization potential, superior electron affinity, lowest electron reorganization energy, as well as highest rate constant of charge hopping, seemed to be the best molecule in terms of its electron-withdrawing abilities in the photoactive layer blend. In addition, in terms of all of the photovoltaic parameters, TP4-TP7 was perceived to be better suited in comparison to TPR. Thus, all our suggested molecules could act as superior acceptors to TPR.

Influence of functional groups in chemical reactivity and optoelectronic properties of novel glycidyl nitrate copolymers (GNCOP): a DFT study.

Nowadays, propulsion materials are receiving increased attention as an important component in electric motors. So, awareness of their chemical reactivity and geometric and electronic structures can help to make materials with higher quality and efficiency. In this study, we have proposed novel glycidyl nitrate copolymers (GNCOPs) and meta-substituted derivatives as propulsion materials. Based on density functional theory (DFT) method, chemical reactivity indices have been calculated for predicting their behavior in burning process. Adding functional groups changes reactivity of the GNCOP compound, especially, in the -CN functional group, chemical potential, chemical hardness, and electrophilicity change -0.374, +0.007, and +1.342eV, respectively. In addition, these compounds have dual properties in interaction with oxygen molecule. Optoelectronic study in time-dependent DFT framework shows that there are three peaks with significant excitations. In conclusion, adding functional group into the GNCOPs can introduce new materials with high energetic properties.

Benchmarking computational chemistry approaches on iminodiacetic acid

In the present study, theoretical harmonic vibrational frequencies (IR and Raman), carbon and proton NMR chemical shifts, geometric parameters, atomic charges (only for heteroatoms), reactivity indices (eLUMO, eHOMO, electronegativity, and hardness), and thermodynamical data (inner energy, enthalpy, Gibbs free energy, and entropy) of iminodiacetic acid (IDA) molecule have been investigated. We utilized ORCA software for B3LYP and HF (combined with Pople and Karlsruhe basis sets) calculations and MOPAC2016 software for semi-empirical calculations (AM1, PM3, and PM6). Theoretical vibrational frequencies and carbon and proton NMR chemical shifts have been compared with the corresponding experimental data. Although there was a strong correlation between the experimental and computational vibrational frequencies at low frequencies (<2200 cm−1), the computational predictions of vibrational frequencies were unsuccessful at high frequencies (>2200 cm−1). Distinctly, the studied computational approaches appeared to perform better in the prediction of carbon and proton NMR chemical shifts. Theoretical vibrational frequencies were also compared to each other to understand the impact of method choice (HF vs B3LYP D3 vs semi-empirical methods), dispersion correction (B3LYP D3 vs B3LYP), water solvation (SMD supplemented vs non-supplemented calculations), the family of basis set (Pople vs Karlsruhe basis sets), numbers of zeta (double vs triple zeta), polarization function (polarized vs nonpolarized basis sets), and diffusion function (diffusion supplemented vs non-supplemented basis sets). Moreover, geometric parameters, heteroatom charges, reactivity indices, and thermodynamical data produced by distinct computational approaches, as well, were compared to each other. Based on these comparisons, we detected critical factors (such as water solvation) acting on the computation of geometries, energies, and charges.

Theoretical investigation by DFT and TDDFT the extension of π-conjugation of novel carbazole-based donor materials for bulk heterojunction organic solar cell applications.

In this study, we have proposed seven designed symmetrical compounds (C2-C8) having a D-π-A-π-D structure based on derivative carbazole as a donor by introducing various π-spacer groups into the reference compound C1-Ref having a D-A-D structure in order to understand the influence of different π-spacers on their efficiency in BHJ solar cells. Various parameters such as geometrical structures, frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP), nonlinear optical properties (NLO), optical properties, light-harvesting efficiency (LHE), reorganization energy, chemical reactivity indices, exciton binding energy (Eb), open-circuit voltage (VOC), and fill-factor (FF) have been investigated using the density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. The results show that the extended π-conjugation of the designed compounds (C2-C8) produces a lower energy gap (Eg), a stronger and broader absorption spectrum, lower reorganization energies and exciton binding, and higher nonlinear optical properties compared to C1-Ref, indicating that these designed compounds are promising as electron donors in BHJ-OSCs. Additionally, the calculated Voc, FF, and LHE of all compounds showed that the C2, C3, C4, C5, and C7 compounds have the best performance in BHJ solar cells compared to the others. In particular, C4 and C5 are excellent candidates for the effective donor materials of BHJ solar cells due to their large Voc, FF, and LHE than the other compounds. This theoretical investigation is expected to provide new strategies to synthesize efficient donor materials for BHJ-OSCs.

Theoretical analysis of the effects of counterions on the supramolecular arrangement of sulfamethoxazole.

Active pharmaceutical ingredients are formulated as the salt form, aiming to modulate their physicochemical properties. In this regard, the optimization and choice of the salt former have a strong influence on toxicity, therapeutic efficiency, and bioavailability. Sulfamethoxazole (SMZ) salts with Na+, Cl-, and Br- counterions influence in the supramolecular arrangement as well as in their thermodynamic and kinetic parameters. Herein, we analyzed the interactions of the Na+, Cl-, and Br- counterions on the supramolecular arrangement of the sulfamethoxazole salts by Hirshfeld surfaces, fingerprint plots, and theoretical methods-quantum theory of atoms in molecules and natural bond orbitals. Moreover, we evaluated their electronic structure by density functional theory using calculation of the frontier molecular orbitals. Molecular electrostatic potential maps were also obtained to predict the interactions of the counterions along crystalline arrangements. We observed that the structures of [SMZ]+ and [SMZ]- ions differ slightly from the SMZ. The chemical reactivity indices show that the SMZ is kinetically more stable than its respective ions, while its anion is more polarizable, and its cation has a higher global electrophilicity index. The molecular electrostatic potential maps show high charge density in the sulfonyl group (nucleophilic region) and the heterocyclic amino group (electrophilic region). Although the molecular skeleton is identical among the three SMZ species and the presence of different counterions in the formation of the crystalline structure of the salts results in supramolecular arrangements with different patterns of intermolecular interactions, despite being very similar in terms of intensities.

Critical analysis of radical scavenging properties of atorvastatin in methanol recently estimated via density functional theory

In this communication we draw attention on serious flaws that plague recently reported antioxidant properties of atorvastatin (ATV) in methanol. First and foremost, we emphasize that the O-H bond dissociation energies (BDE) of about 400kcal/mol previously reported are completely wrong. Further, we present results refuting the previous claim that the proton affinity (PA) of ATV is smaller than that of the ascorbic acid. That unfounded claim relies on incorrect data for PA’s ascorbic acid (which we correct here) circulated in the literature. Further, we correct the values of the chemical reactivity indices (e.g., chemical hardness, electrophilicity index, electroaccepting and electrodonating powers), which were inadequately estimated previously via Kohn–Sham HOMO and LUMO energies. Finally, our updated values for O-H bond dissociation enthalpy (BDE = 91.4kcal/mol) and electron transfer enthalpy (ETE = 105.7kcal/mol) tentatively suggest that direct H-atom transfer (HAT) and sequential proton loss electron transfer (SPLET) may coexist.

New findings on ligand series used as SARS-CoV-2 virus inhibitors within the frameworks of molecular docking, molecular quantum similarity and chemical reactivity indices

Background: The severe acute respiratory syndrome coronavirus (SARS-CoV)-2 virus causes an infectious illness named coronavirus disease 2019 (COVID-19). SARS-CoV is a positive-sense single-stranded RNA virus from the Betacoronavirus genus. The SARS-CoV-2 RNA-dependent RNA polymerase (RdRp) has an important role in the viral life cycle and its active site is a very accessible region, thus a potential therapeutic approach may be to target this region to study the inhibition of viral replication. Various preexisting drugs have been proposed for the treatment of COVID-19 and the use of existing antiviral agents may reduce the time and cost of new drug discoveries, but the efficacy of these drugs is limited. Therefore, the aim of the present study was to evaluate a number of ligands used as SARS-CoV-2 virus inhibitors to determine the suitability of them for potential COVID-19 treatment. Methods: In this study, we selected a series of ligands used as SARS-CoV-2 virus inhibitors such as: abacavir, acyclovir, amprenavir, ascorbic acid vitamin C, azithromycin, baloxavir, boceprevir, cholecalciferol vitamin D, cidofovir, edoxudine, emtricitabine, hydroxychloroquine and remdesivir. These ligands were analyzed using molecular docking, molecular quantum similarity, and chemical reactivity indices defined within a conceptual density functional theory framework. Results: The analysis of molecular quantum similarity indices on inhibitors showed a high number of differences from a structural point of view. However, they are quite similar in their electronic density, obtaining the highest values in the electronic similarity index. Global and local chemical reactivity indices were analyzed. Conclusions: These studies allowed for the identification of the main stabilizing interactions using the crystal structure of SARS-CoV-2 RdRp. The molecular quantum similarity and chemical reactivity descriptors provide novel insights into these ligands that can be used in the design of new COVID-19 treatments.

Computational investigation of the synthesized new indoline-2,3-dione and their derivatives

Computational studies using DFT incorporating the B3LYP/6-311++G(d,p) level is used to predict the stability of the synthesized 1-(5-phenyl-4H-1,2,4-triazol-3-yl)indoline-2,3-dione and its para-substituted (X: -CH3, -F, -CN, -NO2) in different solvents (acetone, ethanol, and methanol) and gas phases. Energetic properties, atomic charges, dipole moments, natural bond orbital (NBO), molecular electrostatic potential (MEP), and frontier molecular orbital (FMO) analyses are studied. The gauge independent atomic orbital (GIAO) method is used to quantify the nuclear magnetic resonance (NMR) chemical shift of the molecules. NBO analysis was used to assess the stability of the considered molecules, as well as their hyperconjugative relationships and electron delocalization. The charge transfer within the molecules is determined using the HOMO and LUMO analyses. The MEP surface was performed by the DFT method to predict the reactive sites for nucleophilic and electrophilic attacks. FMO analysis revealed that compound 5 (X=NO2) has a lower HOMO-LUMO energy (EHL) gaps in the considered phases, and is thus kinetically more stable in different media. Chemical reactivity indices as NO2 &gt; CN &gt; Cl &gt; H &gt; CH3 that predict the lowest (X=CH3) and highest (X=NO2) activity for the studied compounds. The energy difference derived from EHL gap leads to intramolecular hyperconjugative interactions pi→pi*.

A New Schiff Base Molecule Prepared from Pyrimidine-2-thione: Synthesis, Spectral Characterization, Cytotoxic Activity, DFT, and Molecular Docking Studies

Schiff base derivatives are some of the most widely used organic compounds for industrial purposes and they exhibit a broad range of biological activities. In this paper, a new Schiff base derivative (2) synthesized from the condensation reaction of 1-amino-5-benzoyl)-4- phenylpyrimidine-2(1H)-thione (1) with 2-chlorobenzaldehyde. The new compound was characterized by 1H, 13C NMR, and FT-IR. The biological activity property of this compound was tested against two different cancer cell lines and a healthy human cell line. The results demonstrate that molecule 2 has antiproliferative activity. In molecular modeling studies, the interaction site was examined using the epidermal growth factor receptor (EGFR) tyrosine kinase domain. Alignment in molecular docking, surface mapping binding, amino acids, and binding energy calculated. Glide score energy was found to be -9.820 kcal/mol and it predicted that the bonding interaction is strong. Theoretical calculations were made to compare the experimental and theoretical data. These calculations were performed on the 6–31 G* basis set using the Density Functional Theory (DFT) method and Becke-3-Parameter-Lee-Yang-Parr (B3LYP). Using this method, various parameters, such as frontier molecular orbitals, HOMO-LUMO energy levels, band gap, and chemical reactivity indices were found and interpreted.

New Organic Dyes with Low Bandgap Based on Heterocyclic Compounds for Dye-sensitized Solar Cells Applications

In this paper, a theoretical study has been carried out. This study concerns four organic dyes with structure D–π–A on the base of triphenylamine; we choose thiophene and thieno [3, 4-b] pyrazine group as a donor and the group cyanoacrylic acid as an acceptor bridged by four conjugated spacers consisting of phenyl, pyrrole, thiophene, and furan. Our studied dyes' ground state geometric and electronic properties are calculated after optimization in their fundamental states with DFT / B3LYP / 6−311G (d, p). Using this method, EHOMO, ELUMO, bandgap energy, λmax, chemical reactivity indices, dipole moment, the Voc, molecular electrostatic potential (MEP), the LHE, the free injection energy (ΔGinj), the regeneration energy (ΔGreg), and the total reorganization energy (λtot) for all these dyes have been calculated and discussed. The optical properties such as Etr, the maximum wavelength (λmax), and the corresponding oscillator strengths have been carried out by the TD−DFT method at CAM–B3LYP/6–311G (d, p). The calculated results for all these dyes indicate that all these latters can be considered favorable candidates for an efficient DSSC sensitizer.

Electronic properties of amino acids and nucleobases: similarity classes and pairing principles from chemical reactivity indices.

We present a new classification scheme for amino acids and nucleobases based on the electronic properties of the individual molecules. Using chemical reactivity indices such as electronegativity, electrophilicity, and chemical hardness, we can identify similarities and differences between each class of amino acids and nucleobases. Notable differences emerge in particular with regard to high, neutral or low electronegativity as well as different combinations of chemical hardness. Our approach allows us to relate these insights to the properties of the side groups in terms of a unique reference scheme. We further show that hydrophobic differences between amino acids are rather negligible in the context of electronic properties. Our classification scheme also rationalizes the occurrence of distinct stable nucleobase pairs and clearly emphasizes certain differences between individual molecules. The stability and abundant occurrence of Watson-Crick nucleobase pairs is further discussed in the context of the minimum electrophilicity principle.

Corrosion inhibition of mild steel by aminobenzoic acid isomers in hydrochloric acid solution: Efficiency and adsorption mechanisms

Ortho-, meta- and para-aminobenzoic acid (ABA) in hydrochloric acid solution are used as mild steel corrosion inhibitors. Modeled as gas-solid and acidic aqueous-solid interfaces, we investigate their performance and adsorption mechanisms using first principles methodologies and Monte Carlo simulations. Computations show that both neutral and protonated ABAs exhibit spontaneous adsorption on Fe(110) surface, which is dominated by weak interactions. We observed an inhibition efficiency isomeric effect, as established experimentally. Therefore, our work should motivate the extensive use of computational modelling and chemical reactivity indices for in-depth studies of corrosion inhibition of metals by organic compounds as those employed in industries.

Synthesis, characterization, antimicrobial activity and DFT study of some novel Schiff bases

Two new Schiff bases derived from L-cysteine and substituted benzaldehyde were synthesized: the compound 1 [2-((2-chlorobenzylidene) amino)-3-mercaptopropanoic acid] and the compound 2 [3-mercapto-2-((2-methoxybenzylidene) amino) propanoic acid]. Their structures were confirmed by experimental FT-IR, NMR (1H, 13C), and theoretical methodology DFT (density functional theory). DFT calculations were based on global chemical reactivity indices calculated using the B3LYP/6–31G*, B3LYP/6–31G**, and B3LYP/6–31+G* theory levels. Experimentally and theoretically obtained values for FT-IR and NMR (1H, 13C) of test compounds showed good agreement. The reactivity descriptors of B3LYP (E, EHOMO, ELUMO, dipole moment, ∆ɛ, μ, η, ω) were calculated to predict the stability of newly synthesized compounds. The microbiological activity of the compounds was tested on several Gram-positive bacteria: Staphylococcus aureus, Bacillus subtilis, Clostridium sporogenes, Microccocus luteus and Microccocus flavus. The following Gram-negative bacteria were used to test the compounds: Escherichia coli, Pseudomonas aeruginosa Proteus hauseri, Klebsiella pneumoniae, Salmonella enterica subsp. enterica serovar Enteritidis. Also, the activity on the following yeasts was examined: Candida albicans, Saccharomyces cerevisiae and fungal strain Aspergillus brasilliensis. The Schiff base with chlorine in the structure (the compound 1) has the best antimicrobial action against all tested microorganisms. The selected quantum chemical descriptors calculated for the compounds 1 and 2 have a close relationship with the antimicrobial activity.

The theoretical investigation on properties of paeonol and its isomers

Paeonol (2-hydroxy-4-methoxyacetophenone) is the main active ingredient of Traditional Chinese Medicine Moutan Cortex and has a wide range of pharmacological activities. Its isomer 2-hydroxy-5-methoxyacetophenone has also been shown to own the potential for drug. The exploration of the structure and properties of these compounds is helpful for drug design, especially the influence of intramolecular hydrogen bonds on the properties of compounds that medicinal chemists are interested in. In this study, the geometric structure parameters, vibration frequency, topological parameters of electron density, nuclear independent chemical shift, electrostatic potential and reactivity index of paeonol and its isomers in the gas and water phase were calculated by means of quantum chemical calculation (DFT/B3LYP). The equilibrium structure, infrared spectroscopy, intramolecular hydrogen bonding, and reactivity of the two compounds were analysed, and the effect of water solvent was considered. This study reveals the structure and properties of selected compounds at the atomic level and will provide theoretical guidance and inspiration for paeonol-based drug design.

New Chemical Reactivity Index to Assess Alkali–Silica Reactivity

Despite the awareness of the alkali–silica reaction (ASR) since 1940, the need for an efficient and reliable method of evaluating the potential reactivity of aggregates for use in concrete still exists. Current standards to assess the ASR susceptibility of aggregates have limitations due to inherent problems with accelerated testing conditions. This paper introduces a novel chemical reactivity index (RI) to evaluate the alkali–silica reactivity of coarse aggregates or concrete mixtures by exposing samples to a simulated pore solution with composition mimicking that expected in the concrete. Based on the mix design to be evaluated, aggregate samples are exposed to an alkaline solution of appropriate concentration and fixed amounts of CaO. The newly proposed alkali–silica RI is calculated based on the concentrations of silicon, aluminum, and calcium in solution after 21 days of exposure at 55°C. This RI, sensitive to alkali concentration and aggregate mineralogy, exhibited strong agreement with physical expansion.

The optoelectronic properties of π-conjugated organic molecules based on terphenyl and pyrrole for BHJ solar cells: DFT / TD-DFT theoretical study

In the present paper, four π-conjugated materials, based on terphenyl and pyrrole, with A–D–A structure have been theoretically studied to propose new organic compounds to be used in the organic solar cell field. Moreover, the geometrical and optoelectronic properties of the designed molecules M1, M2, M3 and M4 have been computed after optimization in their fundamental states, using the quantum chemical method DFT / B3LYP/ 6−311G (d, p). Different parameters including HOMO and LUMO energy levels, bandgap energy, frontier molecular orbital (FMO), chemical reactivity indices, the density of states (DOS), Voc, electrostatic potential (ESP), and thermodynamic parameters at several temperatures in the range of 0-500 K have been determined. The absorption properties including the transition energy, the wavelengths (λmax), the excitation vertical energy, and the corresponding oscillator strengths of these molecules have been studied using the quantum chemical method TD−DFT / CAM–B3LYP / 6–311G (d, p). The obtained results of our studied compounds show that M3 (with 2H, 2'H-1, 1'-biisoindole moiety) as a donor group has special optoelectronic, absorption, and good photovoltaic characteristics. Thus, they can be utilized as an electron-donating in organic solar cells BHJ type.

Theoretical design of new organic compounds based on diketopyrrolopyrrole and phenyl for organic bulk heterojunction solar cell applications: DFT and TD-DFT study

In this work, a theoretical study of π-conjugated materials based on diphenyl-diketopyrrolo-pyrrole is presented with the aim of proposing new organic materials for BHJ solar cells. Moreover, four compounds M1, M2, M3 and M4 have been reported. The geometric and electronic properties for these studied compounds are calculated after optimization in their fundamental states with DFT / B3LYP / 6 − 311G (d, p). Using this method, several parameters such as frontier molecular orbital, the HOMO and LUMO energies levels, the bandgap, chemical reactivity indices, the Voc and molecular electrostatic potential (MEP) have been discussed. The optical properties such as the transition energy, the wavelengths (λmax), the excitation vertical energy and the corresponding oscillator strengths have been carried out at the ground-state geometries using the TD − DFT method at CAM–B3LYP/6–311G (d, p). This investigation has been used to carry out the next synthesis to compounds more effective as active materials in optoelectronic.

Structural diversity from co-crystal to 1D coordination polymers of 2,6-naphthalenedicarboxylic acid with 4,4′-bipyridine as coligand: structural and computational approach

The co-crystal 2,6-naphthalenedicarboxylic acid (2,6-NDCA) and 4,4′-bipyridine (4,4′-bipy) I and metal (Li+) complex of 2,6-NDCA with 4,4′-bipy i.e. {[Li(2,6-NDC)0.5.(H2O)2] n .4,4′-bipy} II (2,6-NDC = 2,6-naphthalenedicarboxyle) have been characterized by single crystal X-ray diffraction, IR spectra, elemental, and TGA analyses. The co-crystals are stabilized by strong H-bonding between acid–base units whereas the Li+ ion based mixed complex is stabilized by both coordination and H-bonding interactions. During investigation of strong or weak intermolecular interactions, X-ray diffraction analysis and Hirshfeld surface analysis gave rise to comparable results but in the Hirshfeld surface analysis, two-third times more close contacts were observed. Thermogravimetry shows that the complex is stable up to 200 °C after the removal of coordinated water molecules. To get some insights in the chemical reactivity indices, the HOMO-LUMO gap, chemical potential, chemical hardness, and electrophilicity indices for both systems (in gas phase) have been analyzed on the basis of theoretical investigations along with their molecular electrostatic potential surfaces and the total electron density plots; I has been found to be more stable than II which appears to be because of the strong H-bonding interaction(s). The fingerprint plots demonstrate that these weak nonbonding interactions are important for stabilizing the crystal packing.

Theoretical Insights into Specific Ion Effects and Strong-Weak Acid-Base Rules for Ions in Solution: Deriving the Law of Matching Solvent Affinities from First Principles.

We present a detailed study of specific ion effects, volcano plots and the law of matching solvent affinities by means of a conceptual density functional theory (DFT) approach. Our results highlight that specific ion effects and the corresponding implications on the solvation energy are mainly due to differences in the electric chemical potentials and chemical hardnesses of the ions and the solvent. Our approach can be further used to identify reliable criteria for the validity of the law of matching solvent affinities. Basic expressions are derived, which allow us to study the limiting conditions for this empirical observation with regard to matching chemical reactivity indices. Moreover, we show that chaotropic and kosmotropic concepts and their implications for the stability of ion pairs are directly related to a generalized strong and weak acids and bases (SWAB) principle for ions in solution, which is also applicable to rationalize the shape of volcano plots for different solvents. In contrast to previous assumptions, all empirical findings can be explained by the properties of local solvent‐ion complexes which dominate the specific global behavior of ion pairs in solution.

Profiling astrophysically relevant MgC4H chains. An attempt to aid astronomical observations

ABSTRACT In this paper, we report results of an extensive theoretical study on MgC4H chains conducted at DFT and CCSD(T) levels motivated by the recent discovery of this species in IRC+10216. A detailed characterization of both neutral and charged species is presented, which include structural, chemical bonding and vibrational properties, rotational, centrifugal distortion and Watson l-type doubling constants, dipole moments, Fermi contact, and spin-rotation constants. In addition, we present ab initio estimates needed for subsequent astrochemical evolution modelling (e.g. dissociation energies, acidity, electron attachment, and ionization energies and related chemical reactivity indices). Possible formation pathways are also discussed. They comprise exchange, (radiative) association, dissociative recombination, and ion neutralization reactions. As an important result aiming at stimulating further observational searching, we suggest that MgC4H− anions should also be observable via rovibrational spectroscopy. The reason is twofold: (i) Neutral MgC4H0 chains possess a sufficiently large dipole moment consistent with dipole-bound anion states and large electron attachment cross-sections. (ii) MgC4H− anions possess a dipole substantially larger than MgC4H0 neutrals (and also larger than that estimated earlier for the longest astronomically detected C8H− anion). This makes MgC4H− anion intensities in rovibrational spectrum experimentally accessible even in the unlikely case of a relative abundance MgC4H−/MgC4H0 comparable to that of CH4, whose anion has the lowest relative abundance observed so far in space because weakly polar C4H0 chains do not support dipole-bound anion states. A suggestion on why, counterintuitively, the MgC2H abundance found in IRC+10216 was lower than that of the longer MgC4H is also presented.