A Novel Ratiometric Oxygen Sensor Based On a Sextuple Hydrogen‐Bonding Self‐Assembly Molecular Heterodimer

A novel sextuple hydrogen‐bonding (HB) self‐assembly molecular heterodimer bearing an iridium complex as the indicator dye and two carbazoles as the reference dye, namely 6HB‐Irbt‐Cz , was synthesized, and its molecular structure was confirmed by ¹H NMR, ¹³CNMR, TOF‐MS and 2D NMR. Because of the inefficient energy transfer process between the carbazole and iridium complex units, 6HB‐Irbt‐Cz exhibits distinct ?uorescence/phosphorescence dual emission in neat film state. More importantly, the neat film sample of 6HB‐Irbt‐Cz could display linear ratiometric optical response toward oxygen in the full oxygen concentration range from 0 to 100 vol%, together with good stability, reversibility and rapid response‐recovery times. Note that this represents the first discovery of neat‐film‐based oxygen sensor capable of showing strictly linear ratiometric Stern‐Volmer behavior in the oxygen concentration of 0–100 vol%.     

Long‐Lived Charge‐Transfer State Induced by Spin‐Orbit Charge Transfer Intersystem Crossing (SOCT‐ISC) in a Compact Spiro Electron Donor/Acceptor Dyad

We prepared conceptually novel, fully rigid, spiro compact electron donor (Rhodamine B, lactam form, RB)/acceptor (naphthalimide; NI) orthogonal dyad to attain the long‐lived triplet charge‐transfer (³CT) state, based on the electron spin control using spin‐orbit charge transfer intersystem crossing (SOCT‐ISC). Transient absorption (TA) spectra indicate the first charge separation (CS) takes place within 2.5 ps, subsequent SOCT‐ISC takes 8 ns to produce the ³NI* state. Then the slow secondary CS (125 ns) gives the long‐lived ³CT state (0.94 μs in deaerated n‐hexane) with high energy level (ca. 2.12 eV). The cascade photophysical processes of the dyad upon photoexcitation are summarized as ¹NI*→¹CT→³NI*→³CT. With time‐resolved electron paramagnetic resonance (TREPR) spectra, an EEEAAA electron‐spin polarization pattern was observed for the naphthalimide‐localized triplet state. Our spiro compact dyad structure and the electron spin‐control approach is different to previous methods for which invoking transition‐metal coordination or chromophores with intrinsic ISC ability is mandatory.     

Biomimetic Nanocones that Enable High Ion Permselectivity

Artificial counterparts of conical‐shaped transmembrane protein channels are of interest in biomedical sciences for biomolecule detection and selective ion permeation based on ionic size and/or charge differences. However, industrial‐scale applications such as seawater desalination, separation of mono‐ from divalent cations, and treatment of highly‐saline industrial waste effluents are still big challenges for such biomimetic channels. A simple monomer seeding experimental approach is used to grow ionically conductive biomimetic charged nanocone pores at the surface of an acid‐functionalized membrane. These readily scalable nanocone membranes enable ultra‐fast cation permeation (Na⁺=8.4× vs. Mg²⁺=1.4×) and high ion charge selectivity (Na⁺/Mg²⁺=6×) compared to the commercial state‐of‐the‐art permselective membrane (CSO, Selemion, Japan) owing to negligible surface resistance and positively charged conical pore walls.     

Control of Relative Direction and Amplitude in Extension/Contraction Motions of Molecular Strands Induced by Ion Binding

The shape of ligand strands composed of six‐membered aza‐heterocycles (het) connected at the α and α′ positions by hydrazone (hyz) units is determined in a predictable fashion by the nature of the heterocyclic groups (pyridine, pyrimidine, pyrazine etc.), and covers the range from extended linear to compact helical structures. The binding of metal ions to the coordination subunits, defined by the het‐hyz sequences, leads to marked shape changes by inter‐converting bent and linear conformations of the subunits, thus inducing relative motions of strand domains either in the same (con‐sense, “twirling”) or in opposite (dis‐sense, “flapping”) directions. The amplitude of the motion induced by metal‐ion binding and release and the relative directions of the formal motions can be controlled by the nature of the heterocyclic units. Thus, motions around a central 4,6‐disubstituted pyrimidine are dis‐sense motions, whereas there are con‐sense motions around a central 2,5‐disubstituted pyrazine unit, as illustrated by model ligands 1 and 2 , respectively. The more extended helical 3 and undulating (zigzag shape) 4 ligands undergo larger‐amplitude motions combining the relative displacements displayed by 1 and 2 . Ligands 3 and 4 form linear tetranuclear Pb^II and Zn^II complexes, thus producing an extension motion. The same holds for [Ru( 4 )(terpy)₄](PF₆)₈ (terpy=terpyridine). Reversible acid–base‐triggered molecular motions have been generated with [Zn₄( 4 )(OTf)₈] (TfOH=triflic acid).     

A neutralization-reionization and reactivity mass spectrometry study of the generation of neutral hydroxymethylene

Neutral hydroxymethylene HCOH is an important intermediate in several chemical reactions; however, it is difficult to observe due to its high reactivity. In this work, neutral hydroxymethylene and formaldehyde were generated by charge exchange neutralization of their respective ionic counterparts and then were reionized and detected as positive‐ion recovery signals in neutralization–reionization mass spectrometry in a magnetic sector instrument of BEE geometry. The reionized species were characterized by their subsequent collision‐induced dissociation mass spectra. The transient hydroxymethylene neutral was observed to isomerize to formaldehyde with an experimental time span exceeding 13.9 µs. The vertical neutralization energy of the HCOH^+? ion has also been assayed using charge transfer reactions between the fast ions and stationary target gases of differing ionization energy. The measured values match the result of ab initio calculations at the QCISD/6‐311 + G(d,p) and CCSD(T)/6‐311 + + G(3df,2p) levels of theory. Neutral hydroxymethylene was also produced by proton transfer from CH₂OH⁺ to a strong base such as pyridine, confirmed by appropriate isotopic labeling. There is a kinetic isotope effect (KIE) for H⁺ versus D⁺ transfer from the C atom of the hydroxymethyl cation of ～3, consistent with a primary KIE of a nearly thermoneutral reaction. Copyright © 2011 John Wiley & Sons, Ltd.     

Orthogonal Dual‐Triggered Shape‐Memory DNA‐Based Hydrogels

DNA‐based shape‐memory hydrogels revealing switchable shape recovery in the presence of two orthogonal triggers are described. In one system, a shaped DNA/acrylamide hydrogel is stabilized by duplex nucleic acids and pH‐responsive cytosine‐rich, i‐motif, bridges. Separation of the i‐motif bridges at pH 7.4 transforms the hydrogel into a quasi‐liquid, shapeless state, that includes the duplex bridges as permanent shape‐memory elements. Subjecting the quasi‐liquid state to pH 5.0 or Ag⁺ ions recovers the hydrogel shape, due to the stabilization of the hydrogel by i‐motif or C‐Ag⁺‐C bridged i‐motif. The cysteamine‐induced transformation of the duplex/C‐Ag⁺‐C bridged i‐motif hydrogel into a quasi‐liquid shapeless state results in the recovery of the shaped hydrogel in the presence of H⁺ or Ag⁺ ions as triggers. In a second system, a shaped DNA/acrylamide hydrogel is generated by DNA duplexes and bridging Pb²⁺ or Sr²⁺ ions‐stabilized G‐quadruplex subunits. Subjecting the shaped hydrogel to the DOTA or KP ligands eliminates the Pb²⁺ or Sr²⁺ ions from the respective hydrogels, leading to shapeless, memory‐containing, quasi‐liquid states that restore the original shapes with Pb²⁺ or Sr²⁺ ions.     

Supramolecular Organization and Functional Implications of K+ Channel Clusters in Membranes

The segregation of cellular surfaces in heterogeneous patches is considered to be a common motif in bacteria and eukaryotes that is underpinned by the observation of clustering and cooperative gating of signaling membrane proteins such as receptors or channels. Such processes could represent an important cellular strategy to shape signaling activity. Hence, structural knowledge of the arrangement of channels or receptors in supramolecular assemblies represents a crucial step towards a better understanding of signaling across membranes. We herein report on the supramolecular organization of clusters of the K⁺ channel KcsA in bacterial membranes, which was analyzed by a combination of DNP‐enhanced solid‐state NMR experiments and MD simulations. We used solid‐state NMR spectroscopy to determine the channel–channel interface and to demonstrate the strong correlation between channel function and clustering, which suggests a yet unknown mechanism of communication between K⁺ channels.     

Binding of Cationic and Neutral Phenanthridine Intercalators to a DNA Oligomer Is Controlled by Dispersion Energy: Quantum Chemical Calculations and Molecular Mechanics Simulations

Correlated ab initio as well as semiempirical quantum chemical calculations and molecular dynamics simulations were used to study the intercalation of cationic ethidium, cationic 5‐ethyl‐6‐phenylphenanthridinium and uncharged 3,8‐diamino‐6‐phenylphenanthridine to DNA. The stabilization energy of the cationic intercalators is considerably larger than that of the uncharged one. The dominant energy contribution with all intercalators is represented by dispersion energy. In the case of the cationic intercalators, the electrostatic and charge‐transfer terms are also important. The ΔG of ethidium intercalation to DNA was estimated at ?4.5 kcal mol^?1 and this value agrees well with the experimental result. Of six contributions to the final free energy, the interaction energy value is crucial. The intercalation process is governed by the non‐covalent stacking (including charge‐transfer) interaction while the hydrogen bonding between the ethidium amino groups and the DNA backbone is less important. This is confirmed by the evaluation of the interaction energy as well as by the calculation of the free energy change. The intercalation affects the macroscopic properties of DNA in terms of its flexibility. This explains the easier entry of another intercalator molecule in the vicinity of an existing intercalation site.     

The influence of tetraalkylammonium counterions on the conformational transition of an alternating copolymer of maleic acid and n-butyl vinyl ether in aqueous solutions

pH titration curves for the neutralization of an alternating co-polymer of maleic acid and n-butylvinylether (MAnBVE) with tetrabutylammoniumhydroxide (TBAOH) are reported, and compared to the case of neutralization with NaOH or tetraethylammoniumhydroxide (TEAOH). With TBA⁺ counterions the compact form of the polymer is stabilized, remaining the preferred form up to higher net charge densities. This tendency is enhanced at higher temperature. Free energy changes of the conformational transition are higher for TBA⁺ than for TEA⁺ or Na⁺ as counterions.     

Boron as an Electron‐Pair Donor for B⋅⋅⋅Cl Halogen Bonds

MP2/aug′‐cc‐pVTZ calculations were performed to investigate boron as an electron‐pair donor in halogen‐bonded complexes (CO)₂(HB):ClX and (N₂)₂(HB):ClX, for X=F, Cl, OH, NC, CN, CCH, CH₃, and H. Equilibrium halogen‐bonded complexes with boron as the electron‐pair donor are found on all of the potential surfaces, except for (CO)₂(HB):ClCH₃ and (N₂)₂(HB):ClF. The majority of these complexes are stabilized by traditional halogen bonds, except for (CO)₂(HB):ClF, (CO)₂(HB):ClCl, (N₂)₂(HB):ClCl, and (N₂)₂(HB):ClOH, which are stabilized by chlorine‐shared halogen bonds. These complexes have increased binding energies and shorter B?Cl distances. Charge transfer stabilizes all complexes and occurs from the B lone pair to the σ* Cl?A orbital of ClX, in which A is the atom of X directly bonded to Cl. A second reduced charge‐transfer interaction occurs in (CO)₂(HB):ClX complexes from the Cl lone pair to the π* C≡O orbitals. Equation‐of‐motion coupled cluster singles and doubles (EOM‐CCSD) spin–spin coupling constants, ^1xJ(B‐Cl), across the halogen bonds are also indicative of the changing nature of this bond. ^1xJ(B‐Cl) values for both series of complexes are positive at long distances, increase as the distance decreases, and then decrease as the halogen bonds change from traditional to chlorine‐shared bonds, and begin to approach the values for the covalent bonds in the corresponding ions [(CO)₂(HB)?Cl]⁺ and [(N₂)₂(HB)?Cl]⁺. Changes in ¹¹B chemical shieldings upon complexation correlate with changes in the charges on B.     

Electrochemical Modification of Gold Electrodes with Azobenzene Derivatives by Diazonium Reduction

An electrochemical study of Au electrodes electrografted with azobenzene (AB), Fast Garnet GBC (GBC) and Fast Black K (FBK) diazonium compounds is presented. Electrochemical quartz crystal microbalance, ellipsometry and atomic force microscopy investigations reveal the formation of multilayer films. The elemental composition of the aryl layers is examined by X‐ray photoelectron spectroscopy. The electrochemical measurements reveal a quasi‐reversible voltammogram of the Fe(CN)₆^3?/4? redox couple on bare Au and a sigmoidal shape for the GBC‐ and FBK‐modified Au electrodes, thus demonstrating that electron transfer is blocked due to the surface modification. The electrografted AB layer results in strongest inhibition of the Fe(CN)₆^3?/4? response compared with other aryl layers. The same tendencies are observed for oxygen reduction; however, the blocking effect is not as strong as in the Fe(CN)₆^3?/4? redox system. The electrochemical impedance spectroscopy measurements allowed the calculation of low charge‐transfer rates to the Fe(CN)₆^3? probe for the GBC‐ and FBK‐modified Au electrodes in relation to bare Au. From these measurements it can be concluded that the FBK film is less compact or presents more pinholes than the electrografted GBC layer.     

Solid‐State Emission of the Anthracene‐o‐Carborane Dyad from the Twisted‐Intramolecular Charge Transfer in the Crystalline State

The emission process of the o ‐carborane dyad with anthracene originating from the twisted intramolecular charge transfer (TICT) state in the crystalline state is described. The anthracene‐o ‐carborane dyad was synthesized and its optical properties were investigated. Initially, the dyad had aggregation‐ and crystallization‐induced emission enhancement (AIEE and CIEE) properties via the intramolecular charge transfer (ICT) state. Interestingly, the dyad presented the dual‐emissions assigned to both locally excited (LE) and ICT states in solution. From the mechanistic studies and computer calculations, it was indicated that the emission band from the ICT should be attributable to the TICT emission. Surprisingly, even in the crystalline state, the TICT emission was observed. It was proposed from that the compact sphere shape of o ‐carborane would allow for rotation even in the condensed state.     

Reaction model for methane oxidation on reduced SnO2 (110) surface

A reaction model for methane oxidation on a reduced SnO₂ (110) crystal surface has been proposed theoretically using a point‐charge model. The geometric and electronic structures for all the molecules along the four reaction channels have been calculated by means of the MP2/6‐311++G(2d, p) level of theory. On the basis of the optimized geometries in the gas phase, the single‐point calculations of the energies on the point‐charge model are carried out. The results indicate that the energetically favorable reaction paths to yield methanol and formaldehyde on the reduced SnO₂ surface are via the reactant complex CH₃O H₂O and via the secondary production of methanol oxidation, respectively. It is also found that CH₃O⁻ is a stable anion on the surface due to having the high barriers of about 70 kcal/mol in both hydrogen abstraction with O⁻ and thermal decomposition, which is favorable to yield methanol and also is consistent with X‐ray photoelectron spectroscopy (XPS) experiments. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 74: 423–433, 1999     

A quantitative analysis of light‐driven charge transfer processes using voronoi partitioning of time dependent DFT‐derived electron densities

An analytical method is presented that provides quantitative insight into light‐driven electron density rearrangement using the output of standard time‐dependent density functional theory (TD‐DFT) computations on molecular compounds. Using final and initial electron densities for photochemical processes, the subtraction of summed electron density in each atom‐centered Voronoi polyhedron yields the electronic charge difference, Q ^VECD. This subtractive method can also be used with Bader, Mulliken and Hirshfeld charges. A validation study shows Q ^VECD to have the most consistent performance across basis sets and good conservation of charge between electronic states. Besides vertical transitions, relaxation processes can be investigated as well. Significant electron transfer is computed for isomerization on the excited state energy surface of azobenzene. A number of linear anilinepyridinium donor‐bridge‐acceptor chromophores was examined using Q ^VECD to unravel the influence of its pi‐conjugated bridge on charge separation. Finally, the usefulness of the presented method as a tool in optimizing charge transfer is shown for a homologous series of organometallic pigments. The presented work allows facile calculation of a novel, relevant quantity describing charge transfer processes at the atomic level. © 2017 The Authors Journal of Computational Chemistry Published by Wiley Periodicals, Inc.     

Multirotations of (Anilinium)([18]Crown‐6) Supramolecular Cation Structure in Magnetic Salt of [Ni(dmit)2]−

A solid‐state dynamic supramolecular structure consisting of (anilinium)([18]crown‐6) was arranged as the cation in a salt of [Ni(dmit)₂]^? (dmit=2‐thioxo‐1,3‐dithiole‐4,5‐dithiolate). With the ammonium moiety of anilinium located within the cavity of [18]crown‐6, a hydrogen‐bonded supramolecular structure is formed, with an orthogonal arrangement between the π plane of anilinium and the mean O6 plane of [18]crown‐6. In this supramolecular cation, both anilinium and [18]crown‐6 act as dynamic units with different rotational modes in the solid state. The uniform stacks of cations form an antiparallel arrangement, thus producing a layer structure. Sufficient space for the 180° flip‐flop motion of the phenyl ring and the rotation of [18]crown‐6 was observed in the cation layer. Thermally activated 180° flip‐flop motions, with a frequency of 6 MHz at room temperature and an activation energy of 31 kJ mol^?1, were confirmed by temperature‐dependent ²H NMR spectra of ([D₅]anilinium)‐([18]crown‐6)[Ni(dmit)₂]. A double‐minimum potential for the molecular rotation of anilinium, with a barrier of approximately 40 kJ mol^?1, was indicated by ab initio calculations. The wide‐line ¹H NMR spectra indicated a thermally activated rotation of [18]crown‐6 at temperatures above 250 K. Therefore, multiple molecular motions of the 180° flip‐flop motion of the phenyl ring and the rotation of [18]crown‐6 occur simultaneously in the solid state. The temperature‐dependent dielectric constants revealed that the molecular motion of [18]crown‐6, other than the flip‐flop motion, dominates the dielectric response in the measured temperature and frequency range.     

Oligo(p‐phenyleneethynylene) (OPE) Molecular Wires: Synthesis and Length Dependence of Photoinduced Charge Transfer in OPEs with Triarylamine and Diaryloxadiazole End Groups

The systematic synthesis and photophysical, electrochemical and computational studies on an extended series of triphenylamine‐[C?C‐1,4‐C₆H₂(OR)₂]_n‐C?C‐diphenyl‐1,3,4‐oxadiazole dyad molecules (the OR groups are at 2,5‐positions of the para‐phenylene ring and R=C₆H₁₃; n=0–5, compounds 1 , 2 , 3 , 4 and 5 , respectively) are reported. Related molecules with identical end groups, triphenylamine‐C?C‐1,4‐C₆H₂(OR)₂‐C?C‐triphenylamine (R=C₆H₁₃; 6 ) and diphenyl‐1,3,4‐oxadiazole‐[C?C‐C₆H₂(OR)₂]₂‐C?C‐diphenyl‐1,3,4‐oxadiazole (R=C₆H₁₃; 7 ) were also studied. These D–B–A 1 – 5 , D–B–D 6 and A–B–A 7 (D=electron donor, B=bridge, A=electron acceptor) systems were synthesized using palladium‐catalysed cross‐coupling reactions of new p‐phenyleneethynylene building blocks. Steady‐state emission studies on the dyads 1 – 5 reveal a complicated behavior of the emission that is strongly medium dependent. In low polarity solvents the emission is characterized by a sharp high‐energy peak attributed to fluorescence from a locally excited (LE) state. In more polar environments the LE state is effectively quenched by transfer into an intramolecular charge‐transfer (ICT) state. The medium dependence is also observed in the quantum yields (QYs) which are high in cyclohexane and low in acetonitrile, thus also indicating charge‐transfer character. Low‐temperature emission spectra for 2 – 5 in dichloromethane and diethyl ether also reveal two distinct excited states, namely the LE state and the conventional ICT state, depending on solvent and temperature. Hybrid DFT calculations for 1 – 7 establish that the OPE bridge is involved in both frontier orbitals where the bridge character increases as the bridge length increases. Computed TD‐DFT data on 1 – 5 assign the emission maxima in cyclohexane as LE transitions. Each time‐resolved emission measurement on 2 – 7 in cyclohexane and diethyl ether reveals a wavelength dependent bi‐exponential decay of the emission with a fast component in the 5–61 ps range on blue detection and a slower approximately 1 ns phase, independent of detection wavelength. The fast component is attributed to LE fluorescence and this emission component is rate limited and quenched by transfer into an ICT state. The fast LE fluorescence component varies systematically with conjugation length for the series of D–B–A dyads 2 – 5 . An attenuation factor β of 0.15 Å^?1 was determined in accordance with an ICT superexchange mechanism.     

Donnan equilibrium and the effective charge of sodium polyacrylate

Osmometry using an external stressor is a very useful method to measure the equilibrium osmotic pressure for dilute solutions of polyelectrolyte. By taking into account the contribution of the ideal gas law, the excluded volume, the solvency effect, and the Donnan equilibrium effect on the measured pressure it is possible to estimate the effective charge of sodium polyacrylate 35 kgmol⁻¹ as a function of the polymer concentration, the pH, the ionic strength, and the presence of Ca²⁺ ion. The numerical resolution of state equations has shown that the effective charge increases with the ionic strength or with the decreasing polymer concentration, in agreement with recent theoretical models. On the other hand, the effective charge is pH-independent. This statement remains valid as long as the degree of neutralization of the polyacrylate is over 0.5. Above this degree of neutralization, any further neutralization promoted by NaOH addition leads to the condensation of the Na⁺ counterion, in agreement with the general concept of ionic condensation. The effective charge represents only 10–20% of the total number of monomer units for pH within 6 and 9 and ionic strength below 0.1 M. The polymer can tolerate the presence of Ca²⁺ at least up to a molar ratio Ca²⁺/–COOH = 0.222 without any influence on the effective charge. Received: 11 July 2000/Accepted: 23 October 2000     

Controlling the Conformational Changes in Donor–Acceptor [4]‐Dendralenes through Intramolecular Charge‐Transfer Processes

The synthesis of two [4]‐dendralene compounds incorporating thiophene‐(p‐nitrophenyl) donor–acceptor units is presented. The dendralenes adopt two different conformers in solution and solid state and the transformation between the structures can be controlled by light and heat. The electron‐donating components of the dendralenes are represented by bromothienyl (in 13 ) and ethylenedioxythiophene(EDOT)‐thienyl (in 15 ) end‐groups. The most facile transformation involves the isomerisation of donor–acceptor conjugated systems ( a conformers) into structures in which only the thiophenes are conjugated ( b conformers), and this process is driven by ambient light. The structures of the two conformers of compound 13 are confirmed by single‐crystal X‐ray diffraction studies and the structural changes in both compounds have been monitored by ¹H NMR spectroscopy and absorption studies. The transformations were found to be first‐order processes with rate constants of k=0.0027 s^?1 and k=0.00022 s^?1 for 13 and 15 , respectively. Density functional theory calculations at the B3LYP/6‐31G* level give credence to the proposed mechanism for the a → b conversion, which involves photoinduced intramolecular charge transfer (ICT) as the key step. The EDOT derivative ( 15 ) can be polymerised by electrochemical oxidation and a combination of cyclic voltammetry and UV/Vis spectroelectrochemical experiments indicate that the a conformer can be trapped and stabilised in the solid state.     

Tautomers of a Fluorescent G Surrogate and Their Distinct Photophysics Provide Additional Information Channels

Thienoguanosine (^thG) is an isomorphic nucleoside analogue acting as a faithful fluorescent substitute of G, with respectable quantum yield in oligonucleotides. Photophysical analysis of ^thG reveals the existence of two ground‐state tautomers with significantly shifted absorption and emission wavelengths, and high quantum yield in buffer. Using (TD)‐DFT calculations, the tautomers were identified as the H1 and H3 keto‐amino tautomers. When incorporated into the loop of (?)PBS, the (?)DNA copy of the HIV‐1 primer binding site, both tautomers are observed and show differential sensitivity to protein binding. The red‐shifted H1 tautomer is strongly favored in matched (?)/(+)PBS duplexes, while the relative emission of the H3 tautomer can be used to detect single nucleotide polymorphisms. These tautomers and their distinct environmental sensitivity provide unprecedented information channels for analyzing G residues in oligonucleotides and their complexes.     

Effects of Spatial Constraints and Brønsted Acid Site Locations on para‐Terphenyl Ionization and Charge Transfer in Zeolites

The locations of Brønsted acid sites (BAS) in the channels of medium‐pore zeolites have a significant effect on the spontaneous ionization of para‐terphenyl (PP₃) insofar as spatial constraints determine the stability of transition states and charge‐transfer complexes relevant to charge separation. The ionization rates and ionization yield values demonstrate that a strong synergy exists between the H⁺ polarization energy and spatial constraints imposed by the channel topology. Spectroscopic and modeling results show that PP₃ incorporation, charge separation, charge transfer and charge recombination differ dramatically among zeolites with respect to channel structure (H‐FER, H‐MFI, H‐MOR) and BAS density in the channel. Compartmentalization of ejected electrons away from the initial site of ionization decreases dramatically the propensity for charge recombination. The main mode of PP₃^.+ decay is hole transfer to form AlO₄H^.+ ??? PP₃ charge‐transfer complexes characterized by intense absorption in the visible range. According to the nonadiabatic electron‐transfer theory, the small reorganization energy in constrained channels explains the slow hole‐transfer rate.