Primary Ammonium Cations Research Articles

Studying Cation Exchange in {Cr7Co} Pseudorotaxanes: Preparatory Studies for Making Hybrid Molecular Machines.

In the design of dynamic supramolecular systems used in molecular machines, it is important to understand the binding preferences between the macrocycle and stations along the thread. Here, we apply 1H NMR spectroscopy to investigate the relative stabilities of a series of linear alkylammonium templated pseudorotaxanes with the general formula [H2NRR'][Cr7CoF8(O2CCH2 tBu)16] by exchanging the cation in solution. Our results show that the pseudorotaxanes are able to exchange threads via a dissociative mechanism. The position of equilibrium is dependent upon the ammonium cation and solvent used. Short chain primary ammonium cations are shown to be far less favourable macrocycle stations than secondary ammonium cations. Collision-induced dissociation mass spectrometry (CID-MS) has been used to look at disassembly of the pseudorotaxanes in a solvent-free environment and stability trends compared to those in acetone-d6. The energy needed to induce 50 % of the precursor ion loss (E50) is used and shows a similar trend to the equilibria measured by NMR. The relative stabilities of these hybrid inorganic-organic pseudo-rotaxanes are different to those of host-guest compounds involving crown ethers and this may be valuable for the design of molecular machines.

Synthesis of different organic ammonium-based bismuth iodide perovskites for photodetection application.

Bismuth-based perovskites are promising candidates for highly stable halide perovskites with low toxicity. Here, we report the synthesis of a series of bismuth iodide-based perovskites with different primary, secondary, and tertiary ammonium cations and study their structural, thermal, and optical properties, and the likelihood of photodetection. Interestingly, the variation of A-site organic ammonium cations, with different interlayer spacings between adjacent bismuth iodide monolayers, has exotic effects on the diffraction patterns and morphological structures of the perovskite crystals. Thermogravimetric analysis reveals the highest thermal stability of tertiary ammonium-based bismuth perovskite with a decomposition temperature of 385 °C. The branched primary ammonium-based photodetector has photo-responsivity roughly two and four times faster than that of secondary and tertiary ammonium-based devices, respectively. These findings provide insight into the importance of A-site cation engineering for structural modulation and tailoring the optoelectronic properties of bismuth-based perovskites for emerging optoelectronic devices.

2D Hybrid Perovskites Employing an Organic Cation Paired with a Neutral Molecule.

Two-dimensional (2D) hybrid perovskites harness the chemical and structural versatility of organic compounds. Here, we explore 2D perovskites that incorporate both a first organic component, a primary ammonium cation, and a second neutral organic module. Through the experimental examination of 42 organic pairs with a range of functional groups and organic backbones, we identify five crystallization scenarios that occur upon mixing. Only one leads to the cointercalation of the organic modules with distinct and extended interlayer spacing, which is observed with the aid of X-ray diffraction (XRD) pattern analysis combined with cross-sectional transmission electron microscopy (TEM) and elemental analysis. We present a picture in which complementary pairs, capable of forming intermolecular bonds, cocrystallize with multiple structural arrangements. These arrangements are a function of the ratio of organic content, annealing temperature, and substrate surface characteristics. We highlight how noncovalent bonds, particularly hydrogen and halogen bonding, enable the influence over the organic sublattice in hybrid halide perovskites.

Role of Hydrogen Bonding on the Design of New Hybrid Perovskites Unraveled by Machine Learning.

Selecting a set of reactants to accurately design a new low dimensional hybrid perovskite could greatly accelerate the discovery of materials with great potential in photovoltaics, or solid-state lighting. However, this design is challenging as most hybrid metal halides are not perovskites and no feature is clearly associated to the structural characteristics of the inorganic metal halide network. This work first demonstrates that the organic molecules are key parameters to determine the structure type of the inorganic network (i.e., perovskite versus non-perovskite). Then, machine learning (ML) algorithms are used to identify the key features of the organic cations leading to the perovskite structure type. Using a large dataset of hybrid metal halides, this work extracts the organic molecules of all hybrid lead halide compounds, calculates 2756 molecular descriptors and fingerprints for each of these molecules, and are able to predict through ML techniques if a specific organic amine will lead to the perovskite type with an accuracy up to 88.65%. Descriptors related to hydrogen bonding are identified as important features. Thus, a simple but reliable design principle could be demonstrated: the presence of primary ammonium cation is the primary condition to prepare hybrid lead halide perovskites regardless of their dimensionalities.

Archetype-Cation-Based Room-Temperature Ionic Liquid: Aliphatic Primary Ammonium Bis(trifluoromethylsulfonyl)imide as a Highly Functional Additive for a Hole Transport Material in Perovskite Solar Cells.

Room-temperature ionic liquids (RTILs) have attracted significant attention owing to their unique nature and a variety of potential applications. The archetypal RTIL comprising an aliphatic primary ammonium was discovered over a century ago, but this cation is seldom used in modern RTILs because other bulky cations (e.g., quaternary ammonium-, pyridine-, and imidazole-based cations) are prominent in current major applications, such as electrolytes and solvents, which require low and/or reversible reactivities. However, although the design of materials should change according to the intended application, RTIL designs remain conventional even when applied in unexplored fields, limiting their functions. Herein, RTIL consisting of an archetypal aliphatic primary ammonium (i.e., n-octylammonium: OA) cation and a modern bis(trifluoromethylsulfonyl)imide (TFSI) anion is proposed and demonstrated as a highly functional additive for a 2,2',7,7'-tetrakis(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-OMeTAD), which is the most common hole transport material (HTM), in perovskite solar cells (PSCs). The OA-TFSI additive exhibits prominent functions via permanent reactions of the component ions with the PSC components, thus providing several advantages. The OA cations spontaneously and densely passivate the perovskite layer during the HTM deposition process, leading to both suppression of carrier recombination at the HTM/perovskite interface and hydrophobic perovskite surfaces. Meanwhile, the TFSI anions effectively improve the HTM function most likely via efficient stabilization of the Spiro-OMeTAD radical, enhancing hole collection properties in the PSCs. Consequently, PSC performances involving long-term stability were significantly improved using the OA-TFSI additive. Based on the present results, this study advocates that reconsidering the RTIL design, even when it differs from the current major designs yet is suitable for a target application, can provide functions superior to conventional ones. The insights obtained in this work will spur further study of RTIL designs and aid the development of the broad materials science field including PSCs.

Inhibiting Interfacial Diffusion in Heterojunction Perovskite Solar Cells by Replacing Low-Dimensional Perovskite with Uniformly Anchored Quaternized Polystyrene.

Surface heterojunction has been regarded as an effective method to improve the device efficiency of perovskite solar cells. Nevertheless, the durability of different heterojunction under thermal stress is rarely investigated and compared. In this work, benzylammonium chloride and benzyltrimethylammonium chloride are utilized to construct 3D/2D and 3D/1D heterojunctions, respectively. A quaternized polystyrene is synthesized to construct a three-dimensional perovskite/amorphous ionic polymer (3D/AIP) heterojunction. Due to the migration and volatility of organic cations, severe interfacial diffusion is found among 3D/2D and 3D/1D heterojunctions, in which the quaternary ammonium cations in the 1D structure are less volatile and mobile than the primary ammonium cations in the 2D structure. 3D/AIP heterojunction remains intact under thermal stress due to the strong ionic bond anchoring at the interface and the ultra-high molecular weight of AIP. Furthermore, the dipole layer formed by AIP can further reduce the voltage loss caused by nonradiative recombination at the interface by 0.088V. Therefore, the devices based on the 3D/AIP heterojunction achieve a champion power conversion efficiency of 24.27% and maintain 90% of its initial efficiency after either thermal aging for 400h or wet aging for 3000h, showing a great promise for polymer/perovskite heterojunction towards real applications.

Structural Insights into Layered Tetrahalocuprates(II) Based on Small Unsaturated and Cyclic Primary Ammonium Cations.

Layered hybrid halometallates represent a promising class of multifunctional materials, yet with many open challenges regarding the interaction between building blocks. In this work, we present a synthetic and analytical methodology for the efficient synthesis and structural analysis of a series of novel tetrahalocuprate(II) hybrids based on small alkylammonium cations. Observed robustness in geometrical motifs provided a platform for crystal structure determination, even from the complex laboratory powder diffraction data. The slight differences in inorganic layer geometry and severe differences in organic bilayer packing are quantified using well-established descriptors for these materials, and dependences of geometric parameters on anion and cation choice are accounted for. Temperature dependence of structural parameters for one of the tetrachlorocuprate hybrids that was chosen as a model unveils a possible geometrical origin of thermochromism in these materials.

Evaluation of the Stability of Diamine-Appended Mg2(dobpdc) Frameworks to Sulfur Dioxide.

Diamine-appended Mg2(dobpdc) (dobpdc4- = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate) metal-organic frameworks are a promising class of CO2 adsorbents, although their stability to SO2─a trace component of industrially relevant exhaust streams─remains largely untested. Here, we investigate the impact of SO2 on the stability and CO2 capture performance of dmpn-Mg2(dobpdc) (dmpn = 2,2-dimethyl-1,3-propanediamine), a candidate material for carbon capture from coal flue gas. Using SO2 breakthrough experiments and CO2 isobar measurements, we find that the material retains 91% of its CO2 capacity after saturation with a wet simulated flue gas containing representative levels of CO2 and SO2, highlighting the robustness of this framework to SO2 under realistic CO2 capture conditions. Initial SO2 cycling experiments suggest dmpn-Mg2(dobpdc) may achieve a stable operating capacity in the presence of SO2 after initial passivation. Evaluation of several other diamine-Mg2(dobpdc) variants reveals that those with primary,primary (1°,1°) diamines, including dmpn-Mg2(dobpdc), are more robust to humid SO2 than those featuring primary,secondary (1°,2°) or primary,tertiary (1°,3°) diamines. Based on the solid-state 15N NMR spectra and density functional theory calculations, we find that under humid conditions, SO2 reacts with the metal-bound primary amine in 1°,2° and 1°,3° diamine-appended Mg2(dobpdc) to form a metal-bound bisulfite species that is charge balanced by a primary ammonium cation, thereby facilitating material degradation. In contrast, humid SO2 reacts with the free end of 1°,1° diamines to form ammonium bisulfite, leaving the metal-diamine bond intact. This structure-property relationship can be used to guide further optimization of these materials for CO2 capture applications.

The Dynamic Range of Acidity: Tracking Rules for the Unidirectional Penetration of Cellular Compartments.

Labeled ammonium cations with pK a∼7.4 accumulate in acidic organelles because they can be neutralized transiently to cross the membrane at cytosolic pH 7.2 but not at their internal pH<5.5. Retention in early endosomes with less acidic internal pH was achieved recently using weaker acids of up to pK a 9.8. We report here that primary ammonium cations with higher pK a 10.6, label early endosomes more efficiently. This maximized early endosome tracking coincides with increasing labeling of Golgi networks with similarly weak internal acidity. Guanidinium cations with pK a 13.5 cannot cross the plasma membrane in monomeric form and label the plasma membrane with selectivity for vesicles embarking into endocytosis. Self‐assembled into micelles, guanidinium cations enter cells like arginine‐rich cell‐penetrating peptides and, driven by their membrane potential, penetrate mitochondria unidirectionally despite their high inner pH. The resulting tracking rules with an approximated dynamic range of pK a change ∼3.5 are expected to be generally valid, thus enabling the design of chemistry tools for biology research in the broadest sense. From a practical point of view, most relevant are two complementary fluorescent flipper probes that can be used to image the mechanics at the very beginning of endocytosis.

Effect of ionic liquids on the fluorescence properties and aggregation of superfolder green fluorescence protein

Proteins generally tend to aggregate with less desirable properties in numerous solvents, which is one of the major challenges in the development of solvents for functional proteins. This work aims to utilize fluorescence spectroscopy and small angle X-ray scattering (SAXS) to understand the effects of ionic liquids (ILs) on the fluorescence and aggregation behavior of superfolder green fluorescent protein (sfGFP). The studied ILs consisted of four different anions coupled with primary, tertiary and quaternary ammonium cations. The results show that the chromophore fluorescence was generally maintained in 1 mol% IL-water mixtures, then decreased with increasing IL concentration. We primarily employed the pseudo-radius of gyration (pseudo-Rg) to evaluate sfGFP aggregation. The sfGFP was less aggregated with nitrate-based ILs compared to in buffer, and more aggregated in the mesylate-based ILs. Further, we show that the polyol additives of glycerol and glucose in IL-water mixtures slightly decreased the sfGFP propensity to aggregate. Size-exclusion chromatography (SEC)-SAXS was used to characterize the monomeric sfGFP in ethylammonium nitrate (EAN) and triethylammonium mesylate (TEAMs)-water mixtures. The presence of 1 mol% TEAMs maintained the sfGFP fluorescence, promoted the compact structure, but slightly increased the amount of large aggregates, which contrasted with that of EAN.

Amphiphilically Nanostructured Deep Eutectic Solvents.

Deep eutectic solvents (DESs) are neoteric liquids produced by mixing a high-melting-point salt and a molecular hydrogen-bond donor. Amphiphilic (self-assembled) liquid nanostructure, which is key for many of the useful properties of the related ionic liquid class, has not previously been experimentally demonstrated in DESs. Here we show how amphiphilically nanostructured DESs can be prepared using primary ammonium cations. The bulk structure of alkylammonium bromide (alkyl = ethyl-, propyl-, and butyl) and glycerol DESs at a 1:2 mol ratio is examined using neutron diffraction and empirical potential structure refinement fitting. Analysis reveals cation alkyl chain association, which is the signature of amphiphilic liquid nanostructure, in all systems, which becomes better defined with increasing chain length. The ability to form amphiphilically nanostructured DESs will enable the translation of ionic liquid properties associated with liquid nanostructure to DESs.

Understanding the Influence of Key Ionic Liquid Properties on the Hydrolytic Activity of Thermomyces lanuginosus Lipase

AbstractIonic liquids (ILs) are solvents with numerous properties, which have been recently used for enzyme catalysis. In this work, five different ILs based on primary, tertiary, and quaternary ammonium cations coupled with mesylate and propionate anions were used as media for hydrolysis by the industrially relevant enzyme Thermomyces lanuginosus lipase (TLL). We correlated the TLL activity with various key IL and IL–water properties, including ion concentration, water activity (aw), kosmotropicity, hydrogen‐bond basicity (β), and pH. The ion concentration was associated with aw, and the molar ratio of water/IL 5:1 (aw≈0.6) was found to be the threshold for assured TLL activity. Triethylammonium mesylate was the best IL owing to its kosmotropicity and ideal intrinsic β. The pH of IL–water mixtures is a key parameter related to the conformational change of TLL. We demonstrated the pH effect of the IL–water mixtures can be overcome by buffering, and the buffered system displayed the greatest activity.

Carbon Dioxide Retention on Bentonite Clay Adsorbents Modified by Mono-, Di- and Triethanolamine Compounds

A series of organic-inorganic hybrids were developed via intercalation process of primary, secondary and tertiary ammonium cations into different alkali and alkaline earth and transition metal cation forms of bentonite clay to be used as adsorbent materials for CO2capture under ambient temperature and slightly high pressure. The effect of the molar mass of amines on the structural characteristics, surface properties and CO2loading capacity of bentonite clay were investigated by X-ray diffraction, Brunauer-Emmett-Teller method and Magnetic Suspension Balance equipment, respectively. X-ray diffraction results revealed that the basal spacing of bentonite clay after modification with amines was increased with the molar mass of amine used, while BET results showed an inverse effect of the molar mass of amines on the surface area of the synthesized materials. The CO2loading capacity of the examined samples revealed that bentonite clay modified with monoethanolammonium cations retained higher CO2amount compared to those modified with di-and triethanolammonium cations. CO2adsorption isotherms on MEA+-Mg-MMT were conducted at 298, 323 and 348 K and different pressures. A decrease in CO2uptake with increasing temperature was observed, suggesting the exothermic nature of the adsorption process.

Nanostructure changes in protic ionic liquids (PILs) through adding solutes and mixing PILs

The effect of adding primary n-alcohols with aliphatic chains and hexane on the nanostructure of a series of 14 protic ionic liquids (PILs) was explored using small and wide angle X-ray scattering (SAXS and WAXS). PILs were investigated with primary, secondary and tertiary ammonium cations containing different alkyl chain lengths, with and without hydroxyl substitution of the alkyl chain. Formate or nitrate anions were paired with these cations. The PILs which had no identified intermediate range order between 5-16 Å had very low solubilities of the solutes. The other PILs, which had non-polar domains present, were mostly miscible with the primary alcohols of ethanol, propanol and butanol. When the alkyl chain length of the alcohols was similar to the PILs then the alcohols co-partitioned with the alkylammonium cation components of the PILs and caused either an increase or decrease in the size of the non-polar domains, depending on whether the alcohol chain length was longer or shorter than that of the cation in the PIL respectively. For ethylammonium nitrate (EAN) with propanol or butanol and propylammonium nitrate (PAN) with butanol, the difference between the alcohol chain length and the alkyl chain length was too great to lead to a modified nanostructure, and instead large aggregates were present. The solubility of hexane in the alkylammonium nitrate PILs had a very strong correlation to the alkyl chain length. The addition of hexane had very little effect on the non-polar domain sizes, which was attributed to it not being orientated in alignment with the alkylammonium cations in the non-polar domains. Lastly, seven binary PIL-PIL solution series were investigated using SAXS and WAXS to show how the nanostructure of these systems can be fine tuned to control the size and structure of the non-polar domains.

ChemInform Abstract: Catalytic Asymmetric Epoxidation of α‐Branched Enals.

AbstractSalts that consist of a cinchona alkaloid‐derived primary ammonium cation and a chiral phosphate anion catalyze the epoxidation of α‐branched (E)‐α,β‐disubstituted enals with superb enantioselectivity in favor of the trans‐diastereomers.

Centrosymmetric and Noncentrosymmetric R44(12) Rings As Primary Motifs in Salts of Sulfonate Anions and Chiral Primary Ammonium Cations: Their Occurrence in Hydrates, Nonhydrates, and the Zöllner Illusion

The acid−base reaction of naphthalene-1,5-disulfonic acid and naphthalene-2-sulfonic acid with homochiral (R)-1-phenylethylamine or (S)-1-phenylethylamine or heterochiral (RS)-1-phenethylamine give rise to 9 new organic salts: ((R)-1-phenylethylammonium)2•(naphthalene-1,5-disulfonate)•(H2O)2 (2), ((S)-1-phenylethylammonium)2•(naphthalene-1,5-disulfonate)•(H2O)2 (3), ((RS)-1-phenylethylammonium)2•(naphthalene-1,5-disulfonate)•(H2O)2 (4), ((R)-1-phenylethylammonium)2•(naphthalene-1,5-disulfonate) (5), ((S)-1-phenylethylammonium)2•(naphthalene-1,5-disulfonate) (6) ((RS)-1-phenylethylammonium)2•(naphthalene-1,5-disulfonate) (7), ((R)-1-phenylethylammonium)•(naphthalene-2-sulfonate) (8), ((S)-1-phenylethylammonium)•(naphthalene-2-sulfonate) (9) and ((RS)-1-phenylethylammonium)•(naphthalene-2-sulfonate) (10). All nine ammonium sulfonate salts have different 1-D hydrogen bonded columns, some containing water molecules (2−4), which are made up of different sequences of hydrogen bonded rings. The most common hydro...

Inorganic–organic hybrid materials incorporating primary cyclic ammonium cations: The lead bromide and chloride series

Twelve inorganic–organic hybrids have been synthesized and characterised by single-crystal X-ray diffraction experiments. The inorganic component is based on lead(II) bromide and lead(II) chloride units and the organic component on various cyclic hydrocarbons, each with only a primary ammonium group as a ring substituent. When the organic component is cyclopropylammonium, cyclobutylammonium, cyclopentylammonium and cyclohexylammonium, the inorganic motif observed is based on the cubic perovskite structure type and consists of 2-D layers of corner-sharing octahedra, in the ratio of 1 : 2 inorganic–organic. Lead(II) bromide and cycloheptylammonium combined to give 1-D chains of corner-sharing PbBr6 octahedra and similarly, lead(II) bromide and cyclooctylammonium gave 1-D ribbons of corner-sharing PbBr6 octahedra. Lead(II) chloride and cycloheptylammonium have a ribbon motif, and lead(II) chloride and cyclooctylammonium have 2-D layers of corner-, edge- and face-sharing octahedra. These results are compared with a similar study involving lead(II) iodide units and the same set of six cations. General trends and conclusions are discussed.

Topological Classification and Supramolecular Chirality of 21‐Helical Ladder‐Type Hydrogen‐Bond Networks Composed of Primary Ammonium Carboxylates: Bundle Control in 21‐Helical Assemblies

The supramolecular chirality of 1D ladder-type hydrogen-bond networks composed of primary ammonium carboxylates was determined based on topological considerations. Chirality in such networks is based on the absolute configuration of the primary ammonium cation, which arises from discrimination between the two oxygen atoms of the carboxylate anion. The configurations of the cations and anions generate topological diversity in the networks, which are classified into six subgroups. In the Cambridge Structural Database, salts based on ladder type 1 constitute over 70 % of salts with a 1D-ladder-type network. Ladder type 1, based on a 2(1)-axis, is not superimposable on its mirror image, which leads to the first definition of right- or left-handedness of 2(1)-helicity on the basis of supramolecular tilt chirality. Helical assemblies of 2(1)-type with triaxial chirality can be assembled in various ways to yield chiral bundles and crystals. On the basis of these considerations, we constructed clay mimic structures with several bundle patterns by connecting the hydrogen-bond networks by using bifunctional molecules. These results open up the possibility of in-depth crystal engineering based on hydrogen-bond topology.

Liquid Structure and the Ion-Ion Interactions of Ethylammonium Nitrate Ionic Liquid Studied by Large Angle X-Ray Scattering and Molecular Dynamics Simulations

Room temperature ionic liquids (RTILs) are useful as new solvents or materials owing to their favorable properties such as negligible vapor pressure, non-flammability, and wide electrochemical window. For further development of new RTILs, it is indispensable to understand macroscopic properties as solvent and/or liquids of RTILs at a molecular or atomistic level. Here, liquid structure and the ion-ion interactions of room temperature ionic liquid ethylammonium nitrate (EAN) were studied by means of large angle X-ray scattering (LAXS) experiment and molecular dynamics simulations. X-ray interference function for EAN shows a small peak of 0.62 A–1 indicating nano-scale segregation in the ionic liquid. X-ray radial distribution function as the form of D(r) – 4πr2ρ0 evidently shows a peak of 3.4 and broad ones of 4.7, 8 and 12 A, suggesting that EAN has long range ordering in the liquid state. The intra-molecular X-ray interference function was estimated on the basis of molecular geometries found in crystals to yield the inter-molecular X-ray pair correlation functionG_mathrm{inter}mathrm{LAXS}(r). In G_mathrm{inter}mathrm{LAXS}(r), peaks of 3.0, 3.4, and 4.7 A were found as the atom-atom correlation. The peak of 3.0 A can be assigned to the atom-atom correlation of N (C2H5NH3+)mO (NO3–) in the NHmO hydrogen bonding. In addition, the peak of 3.4 A is also ascribable to C (C2H5NH3+)mO (NO3–) correlations in the CHmO interactions. Molecular dynamics simulations based on newly developed force fields to describe a series of primary ammonium cation were performed to ascribe the peaks found in G_mathrm{inter}mathrm{LAXS}(r). The X-ray interference function imathrm{MD}(s) and the pair correlation function Gmathrm{MD}(r) derived from simulations were reasonably in agreement with the experimental ones. According to the partial atom-atom correlation functions derived from the simulations, the experimentally observed peaks of 3.0 and 3.4 A can be ascribable to the NHmO and the CHmO correlations in the closest ethylammonium and nitrate interaction, respectively. The CHmO interactions may play an important role in macroscopic properties of this kind of ionic liquids.

Hydrogen Bonded Semi‐Rigidified Bispyridyl‐Incorporating Aryl Amide Oligomers: Efficient "C"‐Styled Receptors for Aliphatic Ammoniums, a Remarkable Protonation Effect and Chiral Induction

AbstractThe complexing behaviour of two linear compounds 1 and 2 toward the trifluoroacetic acid (TFA) salts of n‐dodecylamine, di‐n‐octylamine, n‐dodecyl D‐ and L‐phenylalaninates (3, 4, and D‐ and L‐5) in chloroform has been described. Compounds 1 and 2 consist of two folded amide moieties with two pyridyls at the terminals which are connected directly or with an acetylene linker. The rigidified folded moieties are stabilized by intramolecular hydrogen bonding, while the whole molecules can adopt an "S"‐ or a "C"‐styled conformation depending on the relative orientation of the two rigidified moieties. 1H NMR, UV‐Vis, fluorescent and circular dichroism investigations revealed that 1 and 2 could bind primary and secondary ammonium cations with their "C"‐styled conformation. In the presence of 1 equiv. of TFA, the binding stability was increased significantly as a result of promoted formation of the "C"‐styled conformation due to the monoprotonation of the peripheral pyridyl units in 1 and 2. In contrast, the addition of 2 equiv. of TFA substantially weakened the binding stability because the "S"‐styled conformation was favored as a result of protonation of both of their pyridyl units. Moreover, remarkable induced circular dichroisms were also displayed for the complexes of 1 and 2 with chiral D‐ and L‐5.