Functional Group Substitution Research Articles

Geometrical benchmarking and analysis of redox potentials of copper(I/II) guanidine-quinoline complexes: Comparison of semi-empirical tight-binding and DFT methods and the challenge of describing the entatic state (part III).

Copper guanidine-quinoline complexes are an important class of bioinorganic complexes that find utilization in electron and atom transfer processes. By substitution of functional groups on the quinoline moiety the electron transfer abilities of these complexes can be tuned. In order to explore the full substitution space by simulations, the accurate theoretical description of the effect of functional groups is essential. In this study, we compare three different methods for the theoretical description of the structures. We use the semi-empirical tight-binding method GFN2-xTB, the density functional TPSSh and the double-hybrid functional B2PLYP. We evaluate the methods on five different complex pairs (Cu(I) and Cu(II) complexes), and compare how well calculated energies can predict the redox potentials. We find even though B2PLYP and TPSSh yield better accordance with the experimental structures. GFN2-xTB performs surprisingly well in the geometry optimization at a fraction of the computational cost. TPSSh offers a good compromise between computational cost and accuracy of the redox potential for real-life complexes.

Functional group substitutions influence the binding of benzophenone-type UV filters with DNA

As a class of possible carcinogens, benzophenone-type UV filters (BPs) widely exist in natural environments and organisms. The crucial step of the carcinogenic process induced by cancerous toxins is binding with DNA to form adducts. Here, the binding of 10 typical BPs, i.e., benzophenone (BP1), 2-hydroxyl benzophenone (BP2), 4-hydroxyl benzophenone (BP3), 2,2′-dihydroxyl benzophenone (BP4), 2,4-dihydroxyl benzophenone (BP5), 4,4′-dihydroxyl benzophenone (BP6), 2,4,4′-trihydroxyl benzophenone (BP7), 2,2′,4,4′-tetrahydroxyl benzophenone (BP8), 2-hydroxyl-4-methoxyl benzophenone (BP9), and 2,2′-dihydroxyl-4-methoxyl benzophenone (BP10), with DNA was tested via fluorescence quenching experiments. Only hydroxyl group-substituted BPs could bind to DNA by groove binding mode, and the quenching constants were 0.93 × 103–5.89 × 103 L/mol. Substituted BPs were preferentially bound to thymine. Circular dichroism analysis confirmed that BPs could affect DNA base stacking but could not transform its B-form. Based on molecular electrostatic surface potential analyses, molecular dynamics simulations, and energy decomposition calculations, it could be found that the site and number of hydroxyl substitution changed the molecular polarity of BPs, thereby affecting the number and strength of hydrogen bonds between BPs and DNA. The hydroxyl substitution at site 2 was more conducive to binding than at site 4. This study is beneficial in comprehending the carcinogenic mechanisms of BPs.

Efficacy of Propyl Selenoethers Against Peroxyl Radical Induced Protein Damage: Effect of Functional Group Substitution

Background: Proteins are the critical bio-molecules for cellular function and are also considered to be highly susceptible to reactive oxygen species (ROS)-induced oxidative damages. Methods: The present study aimed to evaluate some simple water-soluble aliphatic organoselenium compounds bearing different functional groups but of similar carbon chain (propyl) length for a protective effect against 2,2’-azobis-(2-amidinopropane) dihydrochloride (AAPH)-induced oxidative damage using mitochondria as an in vitro model. Results: The results indicated that APPH (20 mM) treatment of mitochondrial fraction induced protein carbonylation, leading to inactivation of redox enzymes and electron transport chain (ETC) and, ultimately the mitochondrial dysfunction. On the other hand, treatment with 0.5 mM of monoselenobutyric acid (SeBA) and monoselenopropyl alcohol (SePOH) significantly prevented APPH-induced protein carbonylation in mitochondrial fraction and restored activities of mitochondrial proteins. On the contrary, monoselenopropyl amine (SePAm) treatment at identical concentrations did not show significant protection to mitochondrial activity from AAPH-induced oxidative damages. The above results concur with the reported peroxyl radical scavenging activities of the above molecules. Conclusion: In conclusion, SeBA and SePOH are potential candidate molecules to protect proteins from oxidative damage and, therefore, can be useful for managing oxidative stress in cellular models.

Elucidation of the Effect of Functional Group Substitution of BN-cyclohexane for Renewable Energy Hydrogen Storage: Density Functional Theory Approach

액상유기수소운반체(liquid organic hydrogen carrier, LOHC)는 액상 형태로 수소를 효율적으로 저장 및 방출할 수 있는 물질로서 미래 수소경제 활성화에 있어서 효과적 수소 저장 물질로 주목받고 있다. 그 중 1,2-BN-cyclohexane 물질은 열역학적으로 안정하며 상온에서의 탈수소화 반응 시 휘발성 오염물질을 방출하지 않는 장점을 가지고 있다. 본 연구에서는 밀도범함수이론(density functional theory, DFT) 계산을 활용하여 1,2-BN-cyclohexane 물질에 기능기 F 및 NH2를 치환하여 더 향상된 가역적 수소 저장 물질로서의 가능성을 평가하고자 하였다. 1,2-BN-cyclohexane 물질의 탈수소화 ∆G는 ‒5.71 kJ/mol인 반면, F-BN-cyclohexane과 NH2-BN-cyclohexane의 탈수소화 ∆G는 각각 ‒4.10과 ‒5.38 kJ/mol으로 나타났다. 탈수소화 ∆G 값이 0 (zero)에 가까울수록 더 가역적인 탈수소화-수소화 반응임을 고려할 때, F와 NH2 기능기로써 치환된 BN-cyclohexane 물질의 가역성이 기존 물질보다 더 향상될 수 있음을 보여주었다. 본 밀도범함수이론(DFT) 연구는 기존 BN-cyclohexane 물질에서 F와 NH2 기능기를 치환함에 따라 향상될 수 있는 탈수소화-수소화 가역적 반응성을 평가하는 체계적 방법론을 제시할 뿐만 아니라, 기존 BN-cyclohexane 물질보다 더 향상된 탈수소화-수소화 반응 가역성을 나타낼 수 있는F-BN-cyclohexane 물질의 제안과 반응 메커니즘에 대한 자세한 정보를 제공해준다.

Chain length effect of spiro-ring N-alkylation on photophysical signalling parameters in Fe(III) selective rhodamine probes.

Manifestation of photophysical signalling parameters in rhodamine derivatives exhibiting complexation induced spiro-ring opening is crucial for the realization of selective metal ion detection at trace levels. Substitution of various functional groups, such as alkylation to the core architecture, modulates the physico-chemical properties of such molecular probes. Despite a few studies, relationships between the extent of photophysical signal modulations and the chain lengths of n-alkyl substituents are still elusive. In this investigation, a few molecular probes based on the rhodamine B (1-5) and rhodamine 6G (6-10) platform were synthesized by their derivatization with n-alkyl substituents of varying chain lengths at the amino-donor of their spiro-ring end, which exhibited Fe(III)-selective absorption and fluorescence 'off-on' signal transduction along with colorization of solution. The Fe(III)-selectivity in these probes remained the same despite their structural distinctions through varied n-alkyl chain lengths of the substituents; however, the quantifiable signalling parameters such as spectroscopic enhancement factors, sensitivity, the kinetics of spiro-ring opening and effectiveness of probe-Fe(III) interactions were analyzed. These parameters were also correlated in terms of the influence of different chain lengths of n-alkyl substituents that efficiently contributed to their inter-componential interactive stereo-electronic environment.

Surface treatment of titanium dioxide nanopowder using rotary electrode dielectric barrier discharge reactor

Titanium dioxide (TiO2) nanopowder (P-25; Degussa AG) was treated using dielectric barrier discharge (DBD) in a rotary electrode DBD (RE-DBD) reactor. Its electrical and optical characteristics were investigated during RE-DBD generation. The treated TiO2 nanopowder properties and structures were analyzed using x-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). After RE-DBD treatment, XRD measurements indicated that the anatase peak theta positions shifted from 25.3° to 25.1°, which can be attributed to the substitution of new functional groups in the TiO2 lattice. The FTIR results show that hydroxyl groups (OH) at 3400 cm−1 increased considerably. The mechanism used to modify the TiO2 nanopowder surface by air DBD treatment was confirmed from optical emission spectrum measurements. Reactive species, such as OH radical, ozone and atomic oxygen can play key roles in hydroxyl formation on the TiO2 nanopowder surface.

Anti-Melanogenic Properties of Velutin and Its Analogs.

Velutin, one of the flavones contained in natural plants, has various beneficial activities, such as skin whitening, as well as anti-inflammatory, anti-allergic, antioxidant, and antimicrobial activities. However, the relationship between the structure of velutin and its anti-melanogenesis activity is not yet investigated. In this study, we obtained 12 velutin derivatives substituted at C5, C7, C3′, and C4′ of the flavone backbone with hydrogen, hydroxyl, and methoxy functionalities by chemical synthesis, to perform SAR analysis of velutin structural analogues. The SAR study revealed that the substitution of functional groups at C5, C7, C3′, and C4′ of the flavone backbone affects biological activities related to melanin synthesis. The coexistence of hydroxyl and methoxy at the C5 and C7 position is essential for inhibiting tyrosinase activity. However, 1,2-diol compounds substituted at C3′ and C4′ of flavone backbone induce apoptosis of melanoma cells. Further, substitution at C3′ and C4′ with methoxy or hydrogen is essential for inhibiting melanogenesis. Thus, this study would be helpful for the development of natural-derived functional materials to regulate melanin synthesis.

INVESTIGATION OF REACTIONS OF INTERACTION OF CELLULOSE NITRIC ESTERS WITH CARBOXYLIC ACID CHLORIDES

The chemical interaction of high-nitrogen cellulose ether with acetic, propionic, butyric and isobutyric acids has been studied. The general laws and features of the electrophilic substitution of functional groups of cellulose nitroesters are revealed. The preferred directions of the chemical interaction of cellulose nitrate with carboxylic acid chlorides are established: O-acylation of nitrate and hydroxyl groups; O-acylation of the glucopyranose ring; O-acylation of the ether bond with depolymerization of the chain of an SC molecule; hydrolysis of nitrate groups; destruction of the chain of a macromolecule of nitric acid ester with the formation of water-soluble organic compounds. The structure, properties and possibilities of using synthesized mixed cellulose ethers were studied. Effective methods have been developed for the chemical modification of cellulose nitrates with carboxylic acid chlorides. The probable directions of the reaction of the interaction of cellulose nitrates with electrophilic reagents are predicted based on quantum-chemical calculations of point charges on the atoms of the reacting molecules. The reactivity of highly substituted cellulose nitrates in reactions with carboxylic acid chlorides has been established. The optimal conditions for the interaction of cellulose nitrates with carboxylic acid chlorides have been identified and a mathematical model of the reaction kinetics has been constructed. The possibility of a directed change in the composition of chemically modified cellulose nitrates depending on the synthesis conditions has been established. As a result of the combined use of physicochemical research methods, the chemical composition was determined and the structure of the synthesized compounds was determined: cellulose acetyl nitrates, cellulose propionyl nitrates, cellulose butyryl nitrates, and cellulose isobutyryl nitrates. Using gel chromatography, it was found that the molecular weight characteristics of the synthesized samples are directly dependent on the conditions of their synthesis. It was found that electrophilic substitution of the functional groups of cellulose nitrate proceeds more intensively in the pyridine medium.

Heterocyclic Compounds: Pharmacology of Pyrazole Analogs From Rational Structural Considerations.

Low quality of life and life-threatening conditions often demand pharmacological screening of lead compounds. A spectrum of pharmacological activities has been attributed to pyrazole analogs. The substitution, replacement, or removal of functional groups on a pyrazole ring appears consistent with diverse molecular interactions, efficacy, and potency of these analogs. This mini-review explores cytotoxic, cytoprotective, antinociceptive, anti-inflammatory, and antidepressant activities of some pyrazole analogs to advance structure-related pharmacological profiles and rational design of new analogs. Numerous interactions of these derivatives at their targets could impact future research considerations and prospects while offering opportunities for optimizing therapeutic activity with fewer adverse effects.

Bright Chromenylium Polymethine Dyes Enable Fast, Four-Color In Vivo Imaging with Shortwave Infrared Detection.

Optical imaging within the shortwave infrared (SWIR, 1000-2000 nm) region of the electromagnetic spectrum has enabled high-resolution and high-contrast imaging in mice, non-invasively. Polymethine dyes, with their narrow absorption spectra and high absorption coefficients, are optimal probes for fast and multiplexed SWIR imaging. Here, we expand upon the multiplexing capabilities in SWIR imaging by obtaining brighter polymethine dyes with varied excitation wavelengths spaced throughout the near-infrared (700-1000 nm) region. Building on the flavylium polymethine dye scaffold, we explored derivatives with functional group substitution at the 2-position, deemed chromenylium polymethine dyes. The reported dyes have reduced nonradiative rates and enhanced emissive properties, enabling non-invasive imaging in mice in a single color at 300 fps and in three colors at 100 fps. Combined with polymethine dyes containing a red-shifted julolidine flavylium heterocycle and indocyanine green, distinct channels with well-separated excitation wavelengths provide non-invasive video-rate in vivo imaging in four colors.

Charge Transport and Optical Absorption Properties of Dibenzocoronene Tetracarboxdiimide Based Liquid Crystalline Molecules: A Theoretical Study.

Structure, optical absorption, and charge transport properties of dibenzocoronene tetracarboxdiimide (DCDI) based molecules were studied using electronic structure calculations. Based on the optimized neutral, cationic, and anionic geometries the ionized state properties, such as ionization potential, electron affinity, hole extraction potential, electron extraction potentials, and reorganization energy, were calculated. On the basis of the ground state geometry of the studied molecules, the absorption spectra were calculated using the time-dependent density functional theory (TDDFT) method at the PBE0/def-TZVP level of theory. It has been observed that the substitution of different functional groups significantly alters the absorption spectra of DCDI. The methoxy- (OCH3-) substituted DCDI molecule has a maximum absorption wavelength of 529 nm. The charge transport parameters, such as the charge transfer integral, spatial overlap integral, and the site energy, are calculated directly from the Kohn-Sham matrix elements. The reorganization energy for the presence of excess positive and negative charges and the charge transfer rate calculated from Marcus' theory were used to find the mobility of charge carriers. The computed results show that the mobility of charge carriers is strongly influenced by the functional groups present on the DCDI molecule. The effect of intermolecular structural fluctuations on charge transport properties was studied through molecular dynamics and Monte Carlo simulations based on the polaron hopping mechanism. The calculated charge carrier mobility shows that the cyano- (CN-) substituted DCDI molecules are having n-type semiconducting property while, methoxy- (OCH3-) and thiol- (SH-) substituted DCDI molecules exhibit ambipolar semiconducting properties.

Study on enhanced mechanical, barrier and optical properties of chemically modified mango kernel starch films

The main aim of this study was to chemically modify mango kernel starch (MKS) and assess its impact on packaging film properties. MKS exhibited limited application due to low solubility, retrogradation, higher gelatinization temperature and hydrophilicity. These limitations could be effectually overcome by integrating modifications to native starch. Chemical modifications of MKS were performed by oxidation and benzylation with a low degree of substitution. X‐ray diffractogram presented A‐type pattern of crystal structure which was in accordance to endosperm starch. Fourier‐transform infrared (FTIR) spectra of the native and modified starch samples exhibited strong bands in the regions corresponding to OH and CH stretching. Additionally, absorption bands were found in the regions for carbonyl and aromatic phenyl vibrations signifying the substitution of functional groups within native starch. Modified starch films presented increased lightness L* representing that the films were lighter in colour than native film. Tensile strength (TS) of modified films was found to increase more than twice that of native starch film. Starch recrystallization was interrupted by oxidation thereby preventing retrogradation. Benzylation lowered the water vapour permeability by 58% and improved UV absorption by 80% when compared with native film.

Theoretical study on the ESIPT processes and fluorescence properties of 2-(1H-Benzimidazol-2-yl)phenol-based derivatives

The molecules based on the excited state intramolecular proton transfer (ESIPT) process are widely used in the fluorescent probes, organic light-emitting diodes and other fields due to their unique optical properties. However, the relationship between the structures and optical properties of ESIPT-based molecules still needs to be further explored. Herein, the effects of different functional groups embedded with the benzene ring on the ESIPT properties and electronic spectra of 2-(1H-Benzimidazol-2-yl)phenol (HBYP)-based derivatives (DPYP, HAYP and HIYP) were explored by using the density functional theory and time-dependent density functional theory methods. Utilizing theoretical calculations, the geometric parameters, including bond lengths and bond angles, infrared vibration spectra, frontier molecular orbitals, potential energy curves as well as topological analysis of the bond critical point of the molecules in the ground and excited states were acquired. The results manifest that the ESIPT process is facile to occur for HBYP and its three derivatives upon the photo-excitation, which can be confirmed by comparing the crucial geometric parameters, IR stretching vibration peaks and energy barriers between the S0 and S1 states. It is worth noting that the molecule HAYP exhibits the largest proton transfer barrier at the S1 state among the studied molecules, and the fluorescence peaks corresponding to its enol and keto forms show the most obvious Stokes shifts of 260 nm and 284 nm, respectively. Therefore, we can deduce that the fluorescence properties can be further affected by regulating the ESIPT characteristics of molecules via the functional group substitution.

Energy levels in dilute-donor organic solar cell photocurrent generation: A thienothiophene donor molecule study

To investigate photocurrent generation mechanisms in these organic solar cells (OSCs), we design and synthesize four thienothiophene (TT)-based small-molecule donors with the highest occupied molecular orbital (HOMO) levels varying from −6.4 eV to −5.1 eV, which span across the HOMO value of the [6,6]-phenyl-C70-butyric acid methyl ester (PC 71 BM) acceptor. We measure TT-based donor:PC 71 BM films’ electronic and optical properties, OSC current density-voltage characteristic, and external quantum efficiency, and perform density functional theory (DFT) calculations. Our results show that photocurrent generation depends strongly on the substitutions of the center TT groups, cyano (-CN) versus hexyloxy (-OHex). With 1 wt% donor, TTOHex:PC 71 BM devices produce seven times, increasing to twelve times for 5 wt % donor, higher photocurrent than neat PC 71 BM devices. In contrast, TTCN:PC 71 BM devices do not generate additional photocurrent even with 10 wt% donor. The photocurrent generation in TT-based donor:PC 71 BM devices depends critically on the HOMO value of the donor molecule with respect to that of PC 71 BM, indicating the importance of type II energy level alignment to facilitate exciton dissociation at the donor-acceptor interface. The photovoltage of all TT:PC 71 BM devices are comparable to neat PC 71 BM devices, 0.85–0.90 V, with a low voltage loss due to non-radiative recombination. The fill factor of TTOHex:PC 71 BM devices are low due to the low hole mobility, ~10 −8 cm 2 /V. Following exciton dissociation, hole transport is analyzed according to three possible mechanisms: tunneling, percolation pathways, and hole back transfer. We find that the hole back transfer mechanism can explain all experimental results and therefore is the primary hole transport mechanism for photocurrent generation in TT-based donor:PC 71 BM dilute-donor OSCs. • Design and synthesis of thienothiophene (TT)-based small molecule donors with varied HOMO levels. • Functional group substitutions on center TT groups have stronger effect on energy levels and photocurrent generation. • Favorable HOMO offset between donor and acceptor is required for exciton dissociation. • Hole back transfer is the primary hole transport mechanism for photocurrent generation in the TT:PCBM dilute-donor devices.

Preparation of magnetic β-cyclodextrin ionic liquid composite material with different ionic liquid functional group substitution contents and evaluation of adsorption performance for anionic dyes

In this study, we successfully prepared two magnetic graphene oxide composites, specifically (mGO@ILs(1)-βCD and mGO@ILs(2)-βCD), with different ionic liquid functional group substitution contents on the β-cyclodextrin (β-CD). Structural characterization of the composite material was performed using Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, specific surface area and pore volume measurements. Comparison of the adsorption performance of the two materials for anionic dyes (lemon yellow (LY), sunset yellow (SY), and ponceau 4R (P4R)) in simulated wastewater. Effect of initial pH value, contact time were studied and discussed in terms of affinity and adsorption efficiency. The adsorption of the anionic azo dye by two adsorbent followed Langmuir adsorption isotherm models and pseudo-second-order kinetics. Noticeably, the maximum adsorption capacity based on the Langmuir model showed that mGO@ILs(2)-βCD was better than mGO@ILs(1)-βCD. Additionally, the adsorbent maintains excellent adsorption capacity after five cycles of adsorption-desorption and has remarkable selective separability. The results showed that the high-density substitution content of the ionic liquid functional groups on β-cyclodextrin in mGO@ILs(2)-βCD is helpful to improve the adsorption capacity and efficiency.

How the functional group substitution and solvent effects affect the antioxidant activity of (+)-catechin?

Based on the density functional theory method, the antioxidant activity of (+)-Catechin (CAT) and its two derivatives, substituted by the electron-donating group -N(CH3)2 (CAT-DA) and electron-withdrawing group -CF3 (CAT-TF), were explored in gas and solvent phases. The parameters related to three antioxidant mechanisms: hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET), were calculated. Results indicate the antioxidant reaction of these three compounds tends to the HAT mechanism in gas phase with the lowest BDE values of 75.2 kcal/mol, 74.4 kcal/mol and 78.6 kcal/mol for CAT, CAT-DA and CAT-TF, respectively, and prefers to the SPLET mechanism in the studied solvents. Furthermore, the increased solvent polarity can promote the expression of SET-PT mechanism, but inhibit the SPLET mechanism. Strikingly, CAT-DA shows the largest the highest occupied molecular orbital energies (−5.317 eV and − 5.570 eV in gas and ethanol phase) and the lowest vertical ionization potentials (6.817 eV and 5.270 eV in gas and water phase) among the three compounds, suggesting that this compound would exhibit the strongest electron-donating ability. The above results mean that introducing the -N(CH3)2 group into the structure of CAT would effectively improve its antioxidant activity, which provides a theoretical reference for the synthesis of more efficient antioxidants.

Tuning electronic structure endows 1,4-naphthoquinones with significantly boosted Zn-ion storage capability and output voltage

Quinone molecular for Zn ion storage typically undergo unsatisfactory capacity and low output voltage because of their poor redox activity of carbonyl group and low redox potential. Here, we demonstrate an energetic strategy to remarkably improve the Zn ion storage capability of 1,4-naphthoquinone by rationally modulating the electronic structure via functional group substitution. The dichloro substituted 1,4-naphthoquinone cathode delivers a high capacity (164.5 mAh g−1 at 0.2 A g−1) and a voltage elevation of 50 mV compared to pristine 1,4-naphthoquinone cathode (12 mAh g−1). Experimental results and density functional theory studies consistently reveal that the introduction of electron-withdrawing Cl substituent can effectively manipulate the electron density of carbonyl carbon and molecular orbital energy levels of 1,4-naphthoquinone, endowing it with higher redox reactivity and discharge plateau. The capability to modulate the electron structure of the quinone cathode by molecular-level designing can provide valuable insights for the development of high-performance zinc battery cathode.

Amino, nitro, chloro, hydroxyl and methyl substitutions may inhibit the binding of PAHs with DNA.

The binding of PAHs with DNA to form PAH-DNA adducts is a crucial step in PAH-induced carcinogenesis. How functional groups affect this binding is largely unknown. Here, we observed that functional group substitutions strongly inhibited PAH-DNA binding. Additionally, -OH substitution has the most potent inhibitory effect as it causes the smallest change in the electrostatic surface potential. Fourier transform infrared spectroscopy and molecular docking analyses demonstrated that PAH derivatives bind with guanine via intercalation and groove binding and then non-specifically insert into the major/minor grooves of DNA. Quantum chemical calculations suggested that hydrogen/halogen bonding may be essential in affecting the binding of functional group-substituted PAHs with DNA. It was further revealed that Log KOA and the PAH derivatives' melting points correlated significantly with binding affinity, implying that changes in the physicochemical characteristics are important factors. This study opens a new window for understanding the relationship between highly toxic PAH derivatives and genetic materials.

Effect of Active Site Modification towards Performance Enhancement in Biopolymer κ-Carrageenan Derivatives.

This research demonstrates a one-step modification process of biopolymer carrageenan active sites through functional group substitution in κ-carrageenan structures. The modification process improves the electronegative properties of κ-carrageenan derivatives, leading to enhancement of the material’s performance. Synthesized succinyl κ-carrageenan with a high degree of substitution provides more active sites for interaction with analytes. The FTIR analysis of succinyl κ-carrageenan showed the presence of new peaks at 1068 cm−1, 1218 cm−1, and 1626 cm−1 that corresponded to the vibrations of C–O and C=O from the carbonyl group. A new peak at 2.86 ppm in 1H NMR represented the methyl proton neighboring with C=O. The appearance of new peaks at 177.05 and 177.15 ppm in 13C NMR proves the substitution of the succinyl group in the κ-carrageenan structure. The elemental analysis was carried out to calculate the degree of substitution with the highest value of 1.78 at 24 h of reaction. The XRD diffractogram of derivatives exhibited a higher degree of crystallinity compared to pristine κ-carrageenan at 23.8% and 9.2%, respectively. Modification of κ-carrageenan with a succinyl group improved its interaction with ions and the conductivity of the salt solution compared to its pristine form. This work has a high potential to be applied in various applications such as sensors, drug delivery, and polymer electrolytes.

Aqueous Diels-Alder reactions for thermochemical storage and heat transfer fluids identified using density functional theory.

Thermal storage and transfer fluids have important applications in industrial, transportation, and domestic settings. Current thermal fluids have relatively low specific heats, often significantly below that of water. However, by introducing a thermochemical reaction to a base fluid, it is possible to enhance the fluid's thermal properties. In this work, density functional theory (DFT) is used to screen Diels-Alder reactions for use in aqueous thermal fluids. From an initial set of 52 reactions, four are identified with moderate aqueous solubility and predicted turning temperature near the liquid region of water. These reactions are selectively modified through 60 total functional group substitutions to produce novel reactions with improved solubility and thermal properties. Among the reactions generated by functional group substitution, seven have promising predicted thermal properties, significantly improving specific heat (by as much as 30.5%) and energy storage density (by as much as 4.9%) compared to pure water.