Resonance-assisted Hydrogen Bond Research Articles

Renewed spectroscopic and theoretical research of hydrogen bonding in ascorbic acid

The studies of two isomers of ascorbic acid and their deuteroanalogues, presented in the paper, have been accomplished by vibrational spectroscopy methods and quantum-chemical simulations. The spectroscopic research of L-ascorbic and D-isoascorbic acids have been carried out by the infrared (IR) and Raman (R) techniques. On the basis of the obtained results the spectral interpretation of the hydrogen bonded groups of ascorbic acids has been performed. Car-Parrinello Molecular Dynamics (CPMD) and Density Functional Theory (DFT) have been employed to support spectroscopic experimental findings and shed light onto the bridged proton dynamics in the L- and D- isomers of ascorbic acids. The accurate assignments of the hydrogen bond modes have been accomplished with the application of deuterosubstitution, CPMD-solid state simulations and Potential Energy Distribution (PED) analysis. The spectral and structural results have shown that dependency ν(OH) = f(γ(OH)) is the most common for the OHO hydrogen bond, whereas dependency d(OO) = f(γ(OH)) differs as for the ionic and resonance assisted hydrogen bonds.

Insights into the role of RAHB and IHB interactions for the structure- Activity relationship of caged xanthone Morellic Acid: Spectroscopic and DFT exploration, molecular docking, and molecular dynamics simulation studies as an Antituberculosis agent

The current study elaborates on experimental and simulated methods using density functional theory (DFT) to analyze the structure, electronic characteristics, and vibrational features of morellic acid, an isolate from Garcinia wightii. The in-depth examination of the stabilized structure indicates that the compound achieves equilibrium through conjugative, hyperconjugative, resonance-assisted hydrogen bonding (RAHB), and intramolecular hydrogen bonding (IHB) interactions, resulting in a well-supported conformation. The vibrational spectra were recorded, and the wavenumbers were comprehensively assigned using Potential Energy Distribution with a scaled quantum mechanical force field. Natural bond orbital (NBO) studies were utilized to calculate donor and acceptor bond interaction energy and electron densities. The TD-DFT computations were performed in solvent (chloroform) and gaseous phase, which agreed with the experimental values. Molecular electrostatic potential (MEP), reduced density gradient (RDG), electron localized function (ELF), and localized orbital locator (LOL) of the molecule were also analyzed. The molecular docking studies revealed that the compound holds great promise as a drug candidate for tuberculosis treatment, with the most thermodynamically stable binding score of -11.542 kcal/mol with 4BFS (protein of Mycobacterium tuberculosis PanK). The molecular dynamics (MD) simulation studies examined the stability and hydrogen bonding system of the ligand-protein complex formed between the molecule and the essential target protein for 100 ns. The findings revealed that the complex remained stable with minimal fluctuations throughout the simulation, suggesting that the molecule may prevent tuberculosis and be used as a treatment candidate.

A homochiral tartrate-bridged dinuclear chromium(III) complex anion with a resonance-assisted hydrogen bond for proton conduction.

The synthesis of a homochiral building block based on L-tartrate-chromium(III) complex anions is reported. The dinuclear complex anion, which contains two bridging L-tartrate ligands and one aromatic N-donor ligand coordinated to chromium(III) ions, exhibits a boat conformation in which intramolecular resonance-assisted hydrogen bonding is present. The sodium L-tartrate-chromium(III) compound with the formula Na[Cr2(bpy)2(L-tart)2H]·9H2O (1) crystallizes from a methanol-water solution as a high water content material in the monoclinic space group P2. The as-synthesized compound is only stable at high relative humidity and undergoes structural transformations during drying, which are accompanied by water loss. However, these transformations are reversible and upon wetting, the material returns to its high water content structure. Based on a combination of experimental techniques (PXRD, in situ ATR-FTIR and EPR spectroscopy), the structure of the complex anions appears to be insensitive to the humidity variable processes (wetting and drying). Due to the presence of several hydrogen acceptor and donor groups in the L-tartrate-chromium(III) complex anion, we investigated the proton transport properties of a sodium L-tartrate-chromium(III) compound by impedance spectroscopy under dry and wet conditions at different temperatures. Since the relative humidity affects the structural transformations in this system, it also has a large influence on the proton conductivity, which varies by up to four orders of magnitude depending on the degree of hydration. These results confirm that the proton conductivity can be tuned in flexible structures in which non-covalent interactions determine the crystal packing.

Theoretical and experimental study of resonance-assisted hydrogen bond in o-hydroxyl diaryl schiff bases

In this paper, the intramolecular hydrogen bond (IMHB) energies (EHB) in fifty 2-OH-XArCH=NArY (2-OH-XBAY) compounds containing resonance-assisted hydrogen bond (RAHB) system and fourteen XArCH=NAr-2′-OH (XBA-2′-OH) compounds without RAHB system were estimated by molecular tailoring approach (MTA) and cis-trans method (CTM) at the theoretical level of DFT B3LYP/6–311++G(d, p). The above compounds were synthesized and their 1H NMR and 13C NMR spectra were determined, then the chemical shifts of H δH on OH and chemical shifts of C δC on CH=N were assigned. The relationship between the δH of the bridged hydrogen atom on OH, the δC of the carbon atom on the CH=N bond in the RAHB ring and the estimated EHB was investigated. The results show that: (1) There is a good linear relationship between the IMHB energy calculated by CTM and that calculated by MTA. (2) There is a good linear relationship between the calculated O-H bond length dO-H and the N···H distance dN···H. (3) For 2-OH-XBAY compounds with fixed X and changing Y, the chemical shift of the bridge hydrogen atom δH(OH) has a good linear relationship with the IMHB energy ECTM, but when both X and Y change, the linear relationship is not good. (4) There is no good linear relationship between the chemical shift of C on CH=N δC(CH=N) and the IMHB energy ECTM. (5) The IMHB energy ECTM of 2-OH-XBAY cannot be expressed by only employing δH(OH), and it is necessary to employ both δH(OH) and δC(CH=N) for expressing their ECTM. (6) As a comparison, there is no RAHB in XBA-2′-OH, and in such case, it is unsuitable to use δH(OH) to express the EHB.

Experimental and theoretical comparison of the vibrational and NMR spectra of novel 6-6’-(1E-1’E)-(Propane-1,3Diylbis (Azanylyidene)) Bis (Phenylmethylylidene)) Bis (3-Octyloxy) Phenol), NBO and molecular docking studies

The characterization study of the synthesized novel compound 6-6’-(1E-1’E)-(Propane-1,3Diylbis(Azanylyidene))Bis(Phenylmethylylidene))Bis(3-Octyloxy)Phenol) (C45H58N2O4) was done by FT-IR, Raman and NMR spectra. Vibrational analysis was realized with normal coordinate treatment, and vibrational modes were assigned in the mid-IR region. The 13C and 1H -NMR spectra of the title compound were measured in DMSO and chloroform, and the corresponding chemical shifts were calculated in the different basis sets (6-31++G(d,p), 6-311G(2d,p), 6-311++G(2d,p), TZVPP) of DFT-B3LYP with continuum models. The vibrational and NMR spectroscopies show that the existence of the intramolecular resonance-assisted hydrogen bonds(O-H...N) results in the redshift of OH vibrational modes and its high proton chemical shifts (ca. 16 ppm), as confirmed by X-ray crystal structure and NRT studies.13C NMR chemical shifts of the Schiff base bond are determined as ca. 174 ppm. The calculations indicate that both the intramolecular hydrogen bond strength and the OH-proton chemical shift increase with increasing solvent polarity. The molecular docking studies reveal that the title ligand has the potency of inhibition against the VIM-2 and NDM-1 active sites of metallo-β-lactamase receptor.

Halogen Bonding in the Decoration of Secondary Coordination Sphere of Zinc(II) and Cadmium(II) Complexes: Catalytic Application in Cycloaddition Reaction of CO2 with Epoxides.

Three new zinc(II) complexes [Zn(H2L3)2(H2O)3] (Zn2), [Zn(H3L2a)(H2O)3]n (Zn3) (H3L2a = 2,4-diiodo-5-(2-(2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene)hydrazineyl)isophthalate) and [Zn(HL4)(DMF)(H2O)]n (Zn4) were synthesized by the reaction of Zn(II) salts with 5-(2-(2,4-dioxopentan-3-ylidene)hydrazineyl) isophthalic acid (H3L3), 2,4,6-triiodo-5-(2-(2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene)hydrazineyl) isophthalic acid (H5L2) (in the presence of NH2OH·HCl) and 5-(2-(2,4-dioxopentan-3-ylidene)hydrazineyl)-2,4,6-triiodoisophthalic acid (H3L4), respectively. According to the X-ray structural analysis, the intramolecular resonance-assisted hydrogen bond ring remains intact, with N···O distances of 2.562(5) and 2.573(5) Å in Zn2, 2.603(6) Å in Zn3, and 2.563(8) Å in Zn4. In the crystal packing of Zn3, the cooperation of I···O and I···I types of halogen bonds between tectons leads to a one-dimensional supramolecular polymer, while I···O interactions aggregate 1D chains of coordination polymer Zn4. These new complexes (Zn2, Zn3, and Zn4) and known [Zn(H3L1)(H2O)2]n (Zn1) (H3L1 = 5-(2-(2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene) hydrazineyl)isophthalate), {[Zn(H3L1)(H2O)3]·3H2O}n (Zn5), [Cd(H3L1)(H2O)2]n (Cd1), {[Cd(HL3)(H2O)2(DMF)]·H2O}n (Cd2), [Cd(H3L3)]n (Cd-3), {[Cd2(μ-H2O)2(μ-H2L4)2(H2L4)2]·2H2O}n (Cd4), and {[Cd(H3L1)(H2O)3]·4H2O}n (Cd5) were tested as catalysts in the cycloaddition reaction of CO2 with epoxides in the presence of tetrabutylammonium halides as the cocatalyst. The halogen-bonded catalyst Zn4 is the most efficient one in the presence of tetrabutylammonium bromide by affording a high yield (85-99%) of cyclic carbonates under solvent-free conditions after 48 h at 40 bar and 80 °C.

Revealing the Reasons for Degeneration of Resonance-Assisted Hydrogen Bond on the Aromatic Platform: Calculations of Ortho-, Meta-, Para-Disubstituted Benzenes, and (Z)-(E)-Olefins

The energies of the O-H∙∙∙O=C intramolecular hydrogen bonds were compared quantitatively for the series of ortho-disubstituted benzenes and Z-isomers of olefins via a molecular tailoring approach. It was established that the hydrogen bond energy in the former series is significantly less than that in the latter one. The reason for lowering the hydrogen bond energy in the ortho-disubstituted benzenes compared to the Z-isomers of olefins is the decrease in the π-contribution to the total energy of the complex interaction, in which the hydrogen bond per se is enhanced by the resonance effect. By the example of the para- and meta-disubstituted benzenes, as well as E-isomers of olefins, it was explicitly shown that the aromatic ring is a much poorer conductor of the resonance effect compared to the double bond. The hydrogen bond in the ortho-disubstituted benzenes has a lower energy than a typical resonance-assisted hydrogen bond because the aromatic moiety cannot properly assist the hydrogen bond with a resonance effect. Thus, a hydrogen bond on an aromatic platform should fall into a special category, namely an aromaticity-assisted hydrogen bond, which is closer by nature to a simple hydrogen bond rather than to a resonance-assisted one.

The effect of resonance-assisted hydrogen bond on the second-order nonlinear optical properties of pyridine hydrazone photoswitches: a quantum chemistry investigation

The combination between photochromic, NLO responses, and RAHB.

Breaking and Formation of Intramolecular Hydrogen Bonds in Dihydroxybenzaldehydes through UV-Induced Conformational Changes in a Low-Temperature Matrix.

Hydrogen bonding (HB) has been receiving attention from both experimental and theoretical researchers since its discovery in the 1920s due to its impact on many chemical and biological processes. However, despite the large number of investigations conducted on this topic, the nature of the HBs and, in particular, the estimation of intramolecular HB energies are still very active subjects of research. In this context, here we report a matrix isolation infrared spectroscopy study of 2,3-dihydroxybenzaldehyde (2,3-DHBA) and 2,4-dihydroxybenzaldehyde (2,4-DHBA), which contain two [one resonance-assisted HB (RAHB) and one conventional HB] and one (RAHB) intramolecular hydrogen bonds, respectively, in their most stable conformer. After isolation of the compounds in cryogenic (15 K) krypton matrices, ultraviolet irradiation led to the formation of higher-energy conformers (by a 180° rotation of the hydroxyl and aldehyde groups), which implies breaking of the intramolecular HBs initially existing in the isolated species and, in the case of 2,3-DHBA, to the formation of a new intramolecular HB. In this way, we were able to manipulate the structure of the molecules, allowing to characterize a diversity of intramolecular HBs in which the OH groups participate (from strong intramolecular RAHBs to weaker conventional HBs, and also no intramolecular HBs) through the corresponding vibrational signatures. The spectroscopic studies were complemented by natural bond orbital analysis and the molecular tailoring approach method, in order to estimate the relative intramolecular HB energies and explore the substitution effects on HB strength.

Probing intra- and inter-molecular interactions through rotational spectroscopy: The case of the odorant 2'-aminoacetophenone and its 1:1 water and neon complexes.

The chirped-pulse Fourier transform microwave spectrum of 2'-aminoacetophenone, an aromatic chemical species with odorant properties, has been recorded in the 2-8GHz frequency range and analyzed, obtaining precise information on the structure of the monomer and its neon and water complexes. The conformation of the monomer is determined by the formation of a resonance-assisted hydrogen bond (RAHB) between the carbonyl and amino groups, which leads to the formation of a bicyclic-like aromatic structure. Accordingly, the cycle formed by the non-covalent bond is preferred to the phenyl ring as the interaction site for neon. In the 1:1 complex, water lies in the molecular plane and forms a strong hydrogen bond with the carbonyl group coupled to an ancillary interaction with the methyl group, leaving the intramolecular RAHB unchanged. The experimental findings are supported by atoms in molecules and symmetry-adapted perturbation theory, which allowed for determining the hydrogen bond and intermolecular interaction energies, respectively.

Resonance-Assisted Hydrogen Bonding and π–π Stacking Modulates the Charge Transfer Coupling in Crystalline Naphthothiazoles

Resonance-Assisted Hydrogen Bonding and π–π Stacking Modulates the Charge Transfer Coupling in Crystalline Naphthothiazoles

Molecular tailoring approach as tool for revealing resonance-assisted hydrogen bond: Case study of Z-pyrrolylenones with the NH⋯OС intramolecular hydrogen bond.

Both the experimental and calculated data reveal that a strong NH⋯OС intramolecular hydrogen bond closing the seven-membered quasi-cycle is formed in the Z-isomers of pyrrolylenones. Comparison of the NH⋯OС intramolecular hydrogen bonds energies in the pyrrolylenones, estimated via the molecular tailoring approach, with the similar data for reference malonaldehydes shows that the resonance-assisted hydrogen bonding occurs in both cases, the hydrogen bond energy being varied mainly within 10-20 kcal/mol. The combined application of function-based and molecular tailoring approaches makes it possible to decompose the NH⋯OС total hydrogen bond energy in the pyrrolylenones into the π- and σ-components. It is established that the contribution of the π-component to the total N(O)H⋯OС hydrogen bond energy in the pyrrolylenones and malonaldehydes is almost the same (6-7kcal/mol). Comparison of the π-contribution to the total energy of the resonance-assisted hydrogen bonding in the Z-isomer of pyrrolylenones with the energy of the push-pull effect in the E-isomer of pyrrolylenones reveals that the resonance contribution to the total energy of the resonance-assisted hydrogen bond in the former significantly enhances with reference to the net resonance energy in the latter. The appearance of the resonance-assisted hydrogen bond in the pyrrolylenones is possible due to the participation in the interaction of 10 or 14 π-electrons satisfying the Hückel aromaticity rule.

Deepening Insights into Near‐Infrared Excited‐State Intramolecular Proton Transfer Lasing: The Charm of Resonance‐Assisted Hydrogen Bonds

AbstractExcited‐state intramolecular proton transfer (ESIPT)‐active organic semiconductor materials, characterized by a or several resonance‐assisted hydrogen bonds (RAHBs), are supposed to be ideal candidates for achieving high‐performance near‐infrared (NIR) lasers. However, according to the energy gap law, the development of ESIPT‐active gain materials is still limited by the serious nonradiative decays. Herein, it is demonstrated that RAHBs can activate ESIPT lasing by inhibiting nonradiative decays. A new ESIPT‐active material 1,5‐dihydroxy‐2,6‐diphenylanthraquinone (DP‐DHAQ) containing two centrosymmetric RAHBs is developed, which exhibits a ≈100‐fold higher radiative decay rate (kr = 1.1 × 1010 s–1) in doped polystyrene (PS) film than that of 1‐hydroxy‐5‐methoxy‐2,6‐diphenylanthraquinone (DP‐HMAQ) and 1,5‐dimethoxy‐2,6‐diphenylanthraquinone (DP‐DMAQ), in which one and two RAHBs are broken, respectively, by introducing methyl groups. Both DP‐DHAQ and DP‐HMAQ can form four‐level systems based on the ESIPT processes, but only DP‐DHAQ doped PS microspheres exhibit laser emission at 710 nm under the test conditions. It is worth mentioning that single‐crystal microplates of DP‐DHAQ can realize NIR laser emission at 725 nm. The results suggest that RAHBs can effectively activate the gain property of ESIPT‐active materials, which deepens insights into NIR ESIPT lasing and provides a new proposal for the design of organic laser‐active molecules.

Intramolecular resonance-assisted hydrogen bonds: Insights from symmetry adapted perturbation theory

The accurate description of hydrogen bonds (H-bonds) is one of the primary challenges when describing intermolecular forces. Intramolecular hydrogen bonds (IMHB) are even more challenging because of their ill-defined energy and their interplay with π-systems. In this contribution, we investigate the role of π-resonance in the enhancement of IMHBs. This is accomplished by comparing a number of π-conjugated systems to their saturated planar counterparts using intramolecular symmetry adapted perturbation theory (I-SAPT). The change in the composition of the IMHB energies (electrostatics, exchange, induction, and dispersion) due to π-conjugation is examined in detail. The biggest changes are observed in the induction and electrostatics contributions. However, electrostatics is nearly canceled by its exchange counterpart. The importance of induction term is also observed when plotting rotational potential curves for the different energy components. Once the distance between the H-bond donor and acceptor is frozen, the stabilization of IMHBs mostly occurs through the decrease in the exchange term leading to less repulsion. In any case, all results are consistent with expected trends in the resonance-assisted hydrogen bonds (RAHBs), and corroborate the fragmentation procedures used in this study. The closeness of induction contribution to the whole interaction energy and the existence of a linear correlation between the IMHB energy and the induction component show that the induction term is a good predictor of the intramolecular RAHBs stability trends.

Tuning the resonance-assisted hydrogen bond (RAHB) of malonaldehyde using π-conjugated substituents and presentation of its energy decomposition

Position of substituents (R1 = H and R2, R3 = H, F, CnHn+1) on malonaldehyde has been changed to amplify its intramolecular hydrogen bonding (IHB) interaction. Results show that π-conjugated substituents at R3 position cause increase of IHB energies of the substituted malonaldehydes. Then, amplification of the IHB interaction in malonaldehyde with C20H21 group at R3 position was verified. Thus, polyethylene chains influence on resonance-assisted hydrogen bond (RAHB) of malonaldehyde and can form malonaldehyde-polyene materials with improved properties. Then, hydrogen bond (HB) interaction of formaldehyde with the substituted malonaldehydes without RAHB ring was studied and HB interaction energies calculated. The HB interaction energies have linear relation with intermolecular hydrogen bond length (dHB). A procedure was employed to estimate IHB energies of the substituted malonaldehydes using the mentioned relation and intramolecular hydrogen bond length (dIHB). Relation between geometrical parameters, spectroscopic data, topological properties, and molecular orbital descriptors with the estimated IHB energies were surveyed. Moreover, IHB energies of the current system were estimated using some quantum chemistry methods to validate the data and find more consistent method with the proposed viewpoint. Results indicated that the estimated IHB energies using proposed procedure have good correlations with other methods. Also, energy decomposition of the IHB interactions in the substituted malonaldehydes was performed using a new method and results showed that electrostatic term has major contribution in the IHB energies.

Benzobisthiazole Polymer with Resonance-assisted Hydrogen Bonds for High-performance Transistor and Solar Cell Applications

Benzobisthiazole Polymer with Resonance-assisted Hydrogen Bonds for High-performance Transistor and Solar Cell Applications

Resonance-Assisted Hydrogen Bond-Revisiting the Original Concept in the Context of Its Criticism in the Literature.

In the presented research, we address the original concept of resonance-assisted hydrogen bonding (RAHB) by means of the many-body interaction approach and electron density delocalization analysis. The investigated molecular patterns of RAHBs are open chains consisting of two to six molecules in which the intermolecular hydrogen bond stabilizes the complex. Non-RAHB counterparts are considered to be reference systems. The results show the influence of the neighbour monomers on the unsaturated chains in terms of the many-body interaction energy contribution. Exploring the relation between the energy parameters and the growing number of molecules in the chain, we give an explicit extrapolation of the interaction energy and its components in the infinite chain. Electron delocalization within chain motifs has been analysed from three different points of view: three-body delocalization between C=C-C, two-body hydrogen bond delocalization indices and also between fragments (monomers). A many-body contribution to the interaction energy as well as electron density helps to establish the assistance of resonance in the strength of hydrogen bonds upon the formation of the present molecular chains. The direct relation between interaction energy and delocalization supports the original concept, and refutes some of the criticisms of the RAHB idea.

Intramolecular resonance assisted N–H⋅⋅⋅O=C hydrogen bond and weak noncovalent interactions in two asymmetrically substituted geminal amido-esters: Crystal structures and quantum chemical exploration

Two asymmetrically substituted geminal amido-esters, namely ethyl (2E)-2-[(2,5-dimethoxy phenyl)carbamoyl]-3-[(4-nitrophenyl)amino] prop-2-enoate (I) and ethyl (2E)-2-[(9,10-dioxo-9,10-dihydroanthracen-1-yl)carbamoyl]-3-(phenylamino) prop-2-enoate (II) were synthesized and the nature and strength of intramolecular resonance assisted hydrogen bond (RAHB) and non-RAHB was studied. X-ray analysis revealed that intramolecular N–H⋅⋅⋅O, and C–H⋅⋅⋅O interactions lead to the formation of angularly fused pseudo tricyclic (A-C) motif in compound I and fused pseudo pentacyclic (A-E) motif in compound II. Intramolecular RAHB; non-RAHB interactions are characterized and quantified by Bader's quantum theory of atoms-in-molecules approach (QTAIM). In both compounds, ring A was found to exhibit intramolecular RAHB characteristics. Crystal structures of I and II are stabilized by weak intermolecular C–H⋅⋅⋅O, C–H⋅⋅⋅π, and π⋅⋅⋅π interactions. Intermolecular interaction energies for different molecular dimers in I and II have been quantified by using the PIXEL, QTAIM, and DFT methods. The pseudoring stacking interaction is observed only in compound II whereas no such stacking interactions are seen in compound I. Hirshfeld surface (HS) analysis suggested that the H⋅⋅⋅H and O⋅⋅⋅H contacts are the first and second dominant contacts in both crystal structures. The theoretical charge density analysis revealed that the C–H⋅⋅⋅O and C–H⋅⋅⋅C(π) interactions produce closed-shell characteristics. Further, the crystal packing of compounds I and II analyzed based on the energy frameworks.

On the Relationship between Hydrogen Bond Strength and the Formation Energy in Resonance-Assisted Hydrogen Bonds.

Resonance-assisted hydrogen bonds (RAHB) are intramolecular contacts that are characterised by being particularly energetic. This fact is often attributed to the delocalisation of electrons in the system. In the present article, we assess this thesis via the examination of the effect of electron-withdrawing and electron-donating groups, namely −F, −Cl, −Br, −CF3, −N(CH3)2, −OCH3, −NHCOCH3 on the strength of the RAHB in malondialdehyde by using the Quantum Theory of Atoms in Molecules (QTAIM) and the Interacting Quantum Atoms (IQA) analyses. We show that the influence of the investigated substituents on the strength of the investigated RAHBs depends largely on its position within the skeleton. We also examine the relationship between the formation energy of the RAHB and the hydrogen bond interaction energy as defined by the IQA method of wave function analysis. We demonstrate that these substituents can have different effects on the formation and interaction energies, casting doubts regarding the use of different parameters as indicators of the RAHB formation energies. Finally, we also demonstrate how the energy density can offer an estimation of the IQA interaction energy, and therefore of the HB strength, at a reduced computational cost for these important interactions. We expected that the results reported herein will provide a valuable understanding in the assessment of the energetics of RAHB and other intramolecular interactions.

A novel bifunctional-group salamo-like multi-purpose dye probe based on ESIPT and RAHB effect: Distinction of cyanide and hydrazine through optical signal differential protocol

A novel bifunctional-group multi-purpose dye probe p-TNS has been designed and synthesized. The probe p-TNS has unique excited-state intramolecular proton transfer (ESIPT) and resonance-assisted hydrogen bonding (RAHB) coupled system, was confirmed to detect cyanide and hydrazine by blocking the ESIPT effect. Cyanide can change the fluorescence of the solution from bright green to orange-red (116 nm Stokes shift), while hydrazine causes the bright green fluorescence to be quenched. The recognition mechanism of the probe p-TNS to CN− and N2H4 was proposed reasonably through spectral characterizations and theoretical calculations. Combined with theoretical calculations, it was speculated that the solvent dependence may be caused by the ICT effect in the molecule. The probe p-TNS could be prepared into test strips for the detection of cyanide and hydrazine. In addition, the probe molecule can also be used to detect trace amounts of cyanide in agricultural products, and respond to gaseous hydrazine by direct contact, indicating that the probe p-TNS has good practical application prospects. Therefore, this molecular framework provides a new way of thinking about detecting multiple target substances.