Intermolecular Electron Transfer Processes Research Articles

Controlled intermolecular proton-coupled electron transfer process: a novel design strategy for highly sensitive piezo-chromic fluorescent materials

Highly sensitive piezochromic fluorescent materials were successfully synthesized via a controlled intermolecular proton-coupled electron transfer process in single-benzene π-system.

Comparison of Computational Strategies for the Calculation of the Electronic Coupling in Intermolecular Energy and Electron Transport Processes.

Electronic couplings in intermolecular electron and energy transfer processes calculated by six different existing computational techniques are compared to nonorthogonal configuration interaction for fragments (NOCI-F) results. The paper addresses the calculation of the electronic coupling in diketopyrrolopyrol, tetracene, 5,5'-difluoroindigo, and benzene-Cl for hole and electron transport, as well as the local exciton and singlet fission coupling. NOCI-F provides a rigorous computational scheme to calculate these couplings, but its computational cost is rather elevated. The here-considered ab initio Frenkel-Davydov (AIFD), Dimer projection (DIPRO), transition dipole moment coupling, Michl-Smith, effective Hamiltonian, and Mulliken-Hush approaches are computationally less demanding, and the comparison with the NOCI-F results shows that the NOCI-F results in the couplings for hole and electron transport are rather accurately predicted by the more approximate schemes but that the NOCI-F exciton transfer and singlet fission couplings are more difficult to reproduce.

Awakening a Molecular Mummy: The Inter-and Intramolecular Photochemistry of Pyromellitic Diimides with Alkyl Carboxylates.

Pyromellitic acid diimides are not as chemically unreactive as conjecturable (and presupposed) from their numerous applications as electron acceptor units or electron carriers in molecular donor-acceptor dyads or triads. Similar to the corresponding phthalimides, electronically excited pyromellitic diimides oxidize alkyl carboxylates in aqueous solution via intermolecular electron transfer (PET) processes, which eventually results in radical-radical combination products, e.g., the benzylation product 6 from N,N'-dimethyl pyromellitic diimide 5. The analogous product 7 was formed with pivalic acid as tert-butyl radical source. One additional product 8 was isolated from alkylation/dearomatization and multiple radical additions, respectively, after prolonged irradiation. In intramolecular versions, from N-carboxyalkylated pyromellitic diimides 9a-e (C1 to C5-spaced), degradation processes were detected, e.g., the cyclization products 10 from the GABA substrate 9c. In sharp contrast to phthalimide photochemistry, the green pyromellitic diimide radical anion was detected here by UV-vis absorption (λabs = 720 nm), EPR (from 9d), and NMR spectroscopy for several intramolecular electron transfer examples. Only the yellow 1,4-quinodial structure is formed from intermolecular PET, which was deduced from the absorption spectra (λabs = 440 nm) and the subsequent chemistry. The pyromellitimide radical anion lives for hours at room temperature in the dark, but is further degraded under photochemical reaction conditions.

Physico-chemical interpretations of the adsorption isotherms of D–π–A sensitizers with pyridyl group on TiO2 for dye sensitized solar cells using statistical physics and density functional theory

In this paper, a statistical physics theory was used to analyze the adsorption isotherms of three Donor (D)-π -Acceptor (A) dyes bearing pyridyl group on TiO2 for dye sensitized solar cells. The experimental data of these organic dyes fit with a monolayer model with two binding sites. Our model is established with the statistical physics approach and contain parameters with a clear physical significance rightly connected to the adsorption mechanism of all adsorbates. The main advantage of this development is to give physical meaning to all involved parameters to be able interpret information about physical adsorption at the molecular level which remains unapproachable by means of empirical methods. The modeling by the adequate model provides new microscopic and macroscopic information included in the adsorption process that did not arise in any case of all previous works. The result shows that the values of adsorption energies proved that a chemisorption process occurred. The density functional theory (DFT) determined the different adsorbed modes, the electronic structure, energy level alignment and electronic density difference maps (EDDs) of the three dyes. The energy levels alignment indicates that the dye regeneration in the NI-4/TiO2 system is the most efficient in DSSCs application. The EDDs showed that the electron density decreases and increases at the dye/TiO2 interface, which is beneficial for the intermolecular electron transfer (IET) process. The DFT calculations support the statistical physics modeling and confirm the strong coordinate bonding between the pyridine ring of dyes NI-4, YNI-1 and YNI-2 and the TiO2 surface.

Acenaphthoquinoxaline Derivatives as Dental Photoinitiators of Acrylates Polymerization.

A series of dyes based on the acenaphthoquinoxaline skeleton was synthesized. Their structure was modified by introducing electron-withdrawing and electron-donating groups, increasing the number of conjugated double bonds and the number and position of nitrogen atoms, as well as the arrangement of aromatic rings (linear or angular). The dyes were investigated as a component in the photoinitiating systems of radical polymerization for a potential application in dentistry. They acted as the primary absorber of visible light and the acceptor of an electron, which was generated from a second component being an electron donor. Thus, the radicals were generated by the photoinduced intermolecular electron transfer (PET) process. Electron donors used differed in the type of heteroatom, i.e., O, S and N and the number and position of methoxy substituents. To test the ability to initiate the polymerization reaction by photoinduced hydrogen atom transfer, we used 2-mercaptobenzoxazole as a co-initiator. The effectiveness of the photoinitiating systems clearly depends on both the modified acenaphthoquinocaline structure and the type of co-initiator. The lower amount of heat released during the chain reaction and the polymerization rate comparable to this achieved for the photoinitiator traditionally used in dentistry (camphorquinone) indicates that the studied dyes may be valuable in this field.

How to Manipulate Through-Space Conjugation and Clusteroluminescence of Simple AIEgens with Isolated Phenyl Rings.

Apart from the traditional through-bond conjugation (TBC), through-space conjugation (TSC) is gradually proved as another important interaction in photophysical processes, especially for the recent observation of clusteroluminescence from nonconjugated molecules. However, unlike TBC in conjugated chromophores, it is still challenging to manipulate TSC and clusteroluminescence. Herein, simple and nonconjugated triphenylmethane (TPM) and its derivatives with electron-donating and electron-withdrawing groups were synthesized, and their photophysical properties were systematically studied. TPM was characterized with visible clusteroluminescence due to the intramolecular TSC. Experimental and theoretical results showed that the introduction of electron-donating groups into TPM could red-shift the wavelength and increase the efficiency of clusteroluminescence simultaneously, due to the increased electronic density and stabilization of TSC. However, TPM derivatives with electron-withdrawing groups showed inefficient or even quenched clusteroluminescence caused by the vigorous excited-state intramolecular motion and intermolecular photoinduced electron transfer process. This work provides a reliable strategy to manipulate TSC and clusteroluminescence.

Laser-Induced Electron Transfer in the Dissociative Multiple Ionization of Argon Dimers.

We report on an experimental and theoretical study of the ionization-fragmentation dynamics of argon dimers in intense few-cycle laser pulses with a tagged carrier-envelope phase. We find that a field-driven electron transfer process from one argon atom across the system boundary to the other argon atom triggers subcycle electron-electron interaction dynamics in the neighboring atom. This attosecond electron-transfer process between distant entities and its implications manifests itself as a distinct phase-shift between the measured asymmetry of electron emission curves of the Ar^{+}+Ar^{2+} and Ar^{2+}+Ar^{2+} fragmentation channels. This letter discloses a strong-field route to controlling the dynamics in molecular compounds through the excitation of electronic dynamics on a distant molecule by driving intermolecular electron-transfer processes.

Effect of graphene between photoanode and sensitizer on the intramolecular and intermolecular electron transfer process.

The main goal of this work is to investigate the effects of a graphene layer between the photosensitive layer and semiconductor substrates on the electron transport performance of dye-sensitized solar cells from the perspective of intramolecular arrangement and interfaces. The benzothiadiazole sensitizer YKP-88 is used as the photosensitive layer and the influence of the graphene layer on the short-circuit current density (Jsc) and open-circuit voltage (Voc) is also discussed by exploring the frontier molecular orbitals, intramolecular charge transfer, weak interaction, interfacial electron dynamic propagations and other microscopic parameters after the anchoring of the graphene layer. The results demonstrate that the graphene layer can accelerate the electron injection of dye molecules into the semiconductor substrate, which not only has a qualitative reduction in injection time, but also has a qualitative change in the increase of the injection amount. In addition, it is also found that the graphene layer increases the stereoscopic effect, the absorption of long wavelength (>700 nm) photon flu and the amount of electron injection into the photoanode, which benefits the intramolecular charge transfer and increases the Jsc and Voc of solar cells. The combination of intermolecular and interfacial perspectives indicates that the appropriate configuration of graphene layers can effectively improve the photoelectric conversion efficiency of dye-sensitized solar cells.

The Green Box: An Electronically Versatile Perylene Diimide Macrocyclic Host for Fullerenes.

The powerful electron accepting ability of fullerenes makes them ubiquitous components in biomimetic donor-acceptor systems that model the intermolecular electron transfer processes of Nature's photosynthetic center. Exploiting perylene diimides (PDIs) as components in cyclic host systems for the noncovalent recognition of fullerenes is unprecedented, in part because archetypal PDIs are also electron deficient, making dyad assembly formation electronically unfavorable. To address this, we report the strategic design and synthesis of a novel large, macrocyclic receptor composed of two covalently strapped electron-rich bis-pyrrolidine PDI panels, nicknamed the "Green Box" due to its color. Through the principle of electronic complementarity, the Green Box exhibits strong recognition of pristine fullerenes (C60/70), with the noncovalent ground and excited state interactions that occur upon fullerene guest encapsulation characterized by a range of techniques including electronic absorption, fluorescence emission, NMR and time-resolved EPR spectroscopies, cyclic voltammetry, mass spectrometry, and DFT calculations. While relatively low polarity solvents result in partial charge transfer in the host donor-guest acceptor complex, increasing the polarity of the solvent medium facilitates rare, thermally allowed full electron transfer from the Green Box to fullerene in the ground state. The ensuing charge separated radical ion paired complex is spectroscopically characterized, with thermodynamic reversibility and kinetic stability also demonstrated. Importantly, the Green Box represents a seminal type of C60/70 host where electron-rich PDI motifs are utilized as recognition motifs for fullerenes, facilitating novel intermolecular, solvent tunable ground state electronic communication with these guests. The ability to switch between extremes of the charge transfer energy continuum is without precedent in synthetic fullerene-based dyads.

A “switch-on” photoluminescent and electrochemiluminescent multisignal probe for hypochlorite via a cyclometalated iridium complex

A new cyclometalated iridium complex, [(bt)2Ir(bpy-Fc)]PF6 (bt = 2-phenylbenzothiazole, bpy-Fc = 4-ferrocenecarbonyl hydrazinocarbonyl-4′-methyl- 2,2′-bipyridine) (probe 1) was designed and synthesized for rapid photoluminescent (PL) and electrochemiluminescent (ECL) sensing of hypochlorite (ClO−). Probe 1 exhibits weak PL and ECL emissions attributed to its electron transfer process. In the presence of ClO−, the cleavage of the hydrazine-linked Fc moiety in probe 1 led to the enhancement of both PL and ECL. The photophysical and ECL properties of probe 1 were investigated and the proposed mechanism of the luminescence enhancement was confirmed by 1H nuclear magnetic resonance spectroscopy, and PL and ECL investigations. In addition, the role of the Fc group in probe 1 in intra- and intermolecular electron transfer processes in the absence and presence of ClO− is demonstrated for both PL and ECL processes. Further, a “switch-on” multi-signal method was developed for sensitive and selective detection of ClO− with detection limits of 466 nM and 302 nM via PL and ECL techniques, respectively. Further, probe 1 was successfully applied for PL imaging of ClO− in living macrophage cells. This work demonstrates that cyclometalated iridium complex bearing recognition and quenching groups is a promising “switch-on” probe in aqueous solutions to image living cells with high sensitivity and selectivity for biomedical applications.

Quantitative Sequential Photoenergy Conversion Process from Singlet Fission to Intermolecular Two-Electron Transfers Utilizing Tetracene Dimer

Singlet fission (SF) theoretically enables the performance of the sequential photoenergy conversion process starting from the singlet state and leading to electron transfer (ET) with the radical ion pair quantum yield approaching 200%. Additionally, the long lifetime of the triplet state opens the possibility for an intermolecular ET process in a diffusion-limited reaction. However, the quantitative two-electron transfer process through SF has yet to be reported. Herein we demonstrate the quantitative sequential process involving SF and leading to intermolecular two-electron transfers using 2,2′-biphenyl-bridged tetracene dimer (Tet-BP-Tet: SF and electron donor) and chloranil (Ch: electron acceptor). The high-yield and long-lived individual triplet excited states of Tet-BP-Tet by SF (ΦT = 175 ± 5% and τT = 0.29 ms) resulted in the quantitative two-electron transfer process (ΦET = 173 ± 5%) with Ch in benzonitrile.

High‐Valent Cobalt‐Catalyzed C−H Activation/Annulation of 2‐Benzamidopyridine 1‐Oxide with Terminal Alkyne: A Combined Theoretical and Experimental Study

AbstractThe multiple possible pathways of high‐valent cobalt catalyzed C−H activation/annulation of 2‐benzamidopyridine 1‐oxide with terminal alkyne were investigated in this combined theoretical and experimental study. The calculated results indicated that CoIII catalyzed C−H activation occurs via a concerted‐metalation deprotonation (CMD) process and that the subsequent annulation involves the CoIV intermediate generated through a proton‐coupled electron transfer (PCET) process in DMSO solvent or through an intermolecular single electron transfer (SET) process in trifluoroethanol (TFE) solvent. Moreover, the theoretical calculations also revealed that CoIII is the actual catalyst, and the solvent controls the chemoselectivity in the annulation stage, triggering a switch between five‐ and six‐membered ring products. Kinetic isotope effect (KIE), electron paramagnetic resonance (EPR), and TEMPO inhibition experiments were performed to confirm the computational results. The mechanistic insights should be valuable for understanding the PCET and SET processes involved in transition metal‐catalyzed C−H functionalizations.magnified image

Immobilization of luminescent Platinum(II) complexes on periodic mesoporous organosilica and their water reduction photocatalysis

Pt(II) complexes have been immobilized on a periodic mesoporous organosilica (PMO) consisting of 2,2′-bipyridine (bpy) units bridged by siloxane bonds (BPy-PMO). Although these Pt(II) complexes are luminescent in their discrete molecular states, the luminescence properties of the immobilized complexes largely depend on the origin of the emission; luminescence is quenched when the emission originates from the 3ππ* excited state of bipyridine due to the coupling of the CH bending vibration of the bpy and the Si-O stretching vibration of the siloxane framework, while luminescence is maintained when the 3ππ* excited state of bipyridine is not the lowest excited state. Although the simple coexistence of Pt(0) nanoparticles and Pt(II) complexes did not catalyze water reduction even in the presence of an electron relay, photocatalytic water reduction is observed when Pt(0)/Pt(II)-co-immobilized BPy-PMOs are used. This result clearly demonstrates the importance of the integration of photosensitizers and catalysts on the PMO for enhancing intermolecular electron-transfer processes.

Impact of newly synthesized water soluble photoluminescent ZnS-L-Cysteine: Core-shell nanoparticles in defining the in-situ opto-electronic orbital model

An intermolecular charge and electron transfer processes in photoluminescent ZnS- L-Cysteine: core-shell Nanoparticles (NPs) extend highly sensitive and variable valence at the core (ZnS)-shell (L-Cysteine) interface primarily due to an extensive mixing of materials frontier orbital (i.e. covalency). Water soluble, ZnS- L-Cysteine: core-shell photo luminescent NPs achieved by straight forward micellar route that is thrust area of research in nanoscience for the control particle size and remarkable properties through chemical co-precipitation method. In the paper we studied, the synthesis of CTAB capped ZnS NPs as well ZnS- L Cysteine: core-shell NPs and examined by their composition, particle size and optical and luminescent properties. The NPs stabilized with CTAB and demonstrated the regular ZnS blue emission on recombination over ZnS band-crevice from shallow electron traps at 490 nm. The onset of the absorption was 80 nm blue shifts moved from 345 nm (bulk) to 265 nm, showing a quantum size impact. Quantum mechanical effect of light applied especially in semiconducting NPs through optoelectronic orbital model, which detect and control the light through electronic devices.

Intra- vs inter-molecular electron transfer processes in C[sbnd]N bond forming reactions. Photochemical, photophysical and theoretical study of 2′-halo-[1,1′-biphenyl]-2-amines

N-Arylation reaction is obtained when 2′-halo-[1,1′-biphenyl]-2-amines are irradiated in basic medium. On the basis of photochemical, photophysical experiments and computational studies we propose that carbazoles are formed by intermolecular electron transfer via SRN1 mechanism.In general, biphenylamines with an EDG like Me or OMe behave in the same way as H giving both, cyclized and reduced products. On the other hand, biphenylamines containing EWG like CN, COOEt or CF3 gave only the corresponding carbazole. Herein, we report for the first time the chain length for the propagation cycle of intramolecular SRN1 reactions and explain that differences in the distribution of products suggest differences regarding the overall mechanism involved.

New insights into the nitroaromatics-detection mechanism of the luminescent metal-organic framework sensor.

Luminescent metal-organic frameworks (LMOFs) have emerged as a group of new and very promising optic sensors in the detection of explosives. However, fundamental understanding of the sensing mechanisms on these materials is still immature and detailed investigations are needed. In this contribution, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) are applied to reveal the underlying principles for the sensing mechanism by comprehensively studying the analyte-sensor interactions. Three molecules namely nitrobenzene, benzene and acetone are chosen as analytes while a newly reported explosives-detecting LMOF [Zn(2)(L)(bipy)(H(2)O)(2)]·(H(2)O)(3)(DMF)(2) is chosen as the sensor. Roles of two fundamental weak interactions namely hydrogen bonding interaction and π-π stacking interaction are clarified for the first time. By studying both the periodic crystal models and cluster models we obtained an in-depth understanding of the detecting mechanism from the view of electronic coupling. We find that intermolecular electron transfer is the inducement for the luminescence quenching detection of explosives. A brand new pathway for this electron transfer process is proposed for the first time. Most significantly, we discover that the hydrogen bond shows multi-functions during the detecting processes which, on the one hand, serves as the electron transfer bridge, and on the other hand, reinforces the π-π stacking. This cooperative effect of the two weak forces inside MOFs is investigated for the first time, which not only provides valuable insights into the understanding of the analyte-sensor interactions inside the sensors but also offers useful guidance in the design of MOF sensors to achieve high sensitivity.

Intermolecular and Intramolecular Electron Transfer Processes from Excited Naphthalene Diimide Radical Anions.

Excited radical ions are interesting reactive intermediates owing to powerful redox reactivities, which are applicable to various reactions. Although their reactivities have been examined for many years, their dynamics are not well-defined. In this study, we examined intermolecular and intramolecular electron transfer (ET) processes from excited radical anions of naphthalene-1,4,5,8-tetracarboxydiimide (NDI(•-)*). Intermolecular ET processes between NDI(•-)* and various electron acceptors were confirmed by transient absorption measurements during laser flash photolysis of NDI(•-) generated by pulse radiolysis. Although three different imide compounds were employed as acceptors for NDI(•-)*, the bimolecular ET rate constants were similar in each acceptor, indicating that ET is not the rate-determining step. Intramolecular ET processes were examined by applying femtosecond laser flash photolysis to two series of dyad compounds, where NDI was selectively reduced chemically. The distance dependence of the ET rate constants was described by a β value of 0.3 Å(-1), which is similar or slightly smaller than the reported values for donor-acceptor dyads with phenylene spacers. Furthermore, by applying the Marcus theory to the driving force dependence of the ET rate constants, the electronic coupling for the present ET processes was determined.

Mechanistic studies of photoinduced intramolecular and intermolecular electron transfer processes in RuPt-centred photo-hydrogen-evolving molecular devices

The photoinduced electron transfer properties of two photo-hydrogen-evolving molecular devices (PHEMDs) [(bpy)2Ru(II)(phen-NHCO-bpy-R)Pt(II)Cl2](2+) (i.e., condensation products of [Ru(bpy)2(5-amino-phen)](2+) and (4-carboxy-4′-R-bpy)PtCl2; bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline; RuPt-COOH for R = COOH and RuPt-CN for R = CN) were investigated. RuPt-CN demonstrates higher photocatalytic performance relative to RuPt-COOH arising from a larger driving force for the intramolecular photoinduced electron transfer (PET) associated with a stronger electron-withdrawing effect of R (ΔGPET = −0.43 eV for RuPt-CN and −0.16 eV for RuPt-COOH). This is the first study on PET events using ultrafast spectroscopy. Dramatic enhancement is achieved in the rate of PET in RuPt-CN (1.78 × 1010 s(−1)) relative to RuPt-COOH (3.1 × 109 s(−1)). For each system, the presence of three different conformers giving rise to three different PET rates is evidenced, which are also discussed with the DFT results. Formation of a charge-separated (CS) state [(bpy)2Ru(III)(phen-NHCO-bpy(−˙)-R)Pt(II)Cl2](2+) in the sub-picosecond time regime and recombination in the picosecond time regime are characterized spectrophotometrically. The CS-state formation was found to compete with reductive quenching of the triplet excited state by EDTA whose dianionic form ion-pairs with dicationic RuPt-COOH. Thus, a key intermediate [(bpy)2Ru(II)(phen-NHCO-bpy(−˙)-R)Pt(II)Cl2](+) (i.e., the one-electron-reduced species) prior to the H2 formation was found to be formed either via reduction of the CS state by EDTA or via formation of [(bpy)2Ru(II)(phen(−˙)-NHCO-bpy-R)Pt(II)Cl2](+) by reductive quenching of the triplet excited state. More importantly, it is also shown that some of the conformers in solution possess a CS lifetime sufficiently long to drive hydrogen evolution from water.

Reconstitution of supramolecular organization involved in energy metabolism at electrochemical interfaces for biosensing and bioenergy production

How the redox proteins and enzymes involved in bioenergetic pathways are organized is a relevant fundamental question, but our understanding of this is still incomplete. This review provides a critical examination of the electrochemical tools developed in recent years to obtain knowledge of the intramolecular and intermolecular electron transfer processes involved in metabolic pathways. Furthermore, better understanding of the electron transfer processes associated with energy metabolism will provide the basis for the rational design of biotechnological devices such as electrochemical biosensors, enzymatic and microbial fuel cells, and hydrogen production factories. Starting from the redox complexes involved in two relevant bacterial chains, i.e., from the hyperthermophile Aquifex aeolicus and the acidophile Acidithiobacillus ferrooxidans, examination of protein-protein interactions using electrochemistry is first reviewed, with a focus on the orientation of a protein on an electrochemical interface mimic of a physiological interaction between two partners. Special attention is paid to current research in the electrochemistry of essential membrane proteins, which is one mandatory step toward the understanding of energy metabolic pathways. The complex and challenging architectures built to reconstitute a membrane-like environment at an electrode are especially considered. The role played by electrochemistry in the attempt to consider full bacterial metabolism is finally emphasized through the study of whole cells immobilized at electrodes as suspensions or biofilms. Before the performances of biotechnological devices can be further improved to make them really attractive, questions remain to be addressed in this particular field of research. We discuss the bottlenecks that need to be overcome in the future.

On the Mechanism of Synergistic Cytotoxicity of Vitamins C and K3: Experiments in Vitro and Quantum-Chemical Analysis

Most patients with hepatocellular carcinoma are inoperable and hepatoma cells are resistant to conventional chemotherapies. So, it is important to develop novel therapies. Treatment of mouse hepatoma MH-22A cells by vitamins C and K3 at the ratio of 100:1 greatly enhanced their cytotoxicity. When cells were subjected to vitamin C at 200 μM or K3 at 2 μM separately, viability was more than 90%. However, when vitamins C and K3 were combined at these concentrations, less than 10% of cells survived.To elucidate the mechanism of this synergy, theoretical quantum-chemical analysis of the dynamics of intermolecular electron transfer (IET) processes within the complexes containing C and K3 was carried out. Optimization of the ground state complex geometry was provided by means of GAUSSIAN03 package. Simulation of the IET was done using NUVOLA package, in the framework of molecular orbitals. Rate of IET was calculated using Fermi Golden rule.Two concurrent pathways of a plausible mechanism of the synergistic action of vitamins C and K3 were analyzed: increasing of acidity in the near surrounding of complex significantly affects redox-cycling and creating the most stable [C2K] complex stabilizes acidity at a high level.Out of the complexes of vitamin K3 with five different forms of vitamin C, the most stable one was the complex with de-hydro-ascorbic acid [C2K], and the second one - with ascorbic acid [C1K]. The spectra of IET represent the different nature of complexes. There are several possibilities for electron transfer in the less stable [C1K] complex, while for the most stable [C2K] complex; the number of resonant states significantly decreases. This confirms that the creation of complex [C1K] escalates increasing of acidity.