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The I 3 − molecule is known to undergo substantial structural reorganization upon solvation by a protic solvent, e.g., water. However, the details of this process are still controversially discussed in the literature. In the present study, we combined experimental and theoretical efforts to disentangle this controversy. The valence (5p), N 4 , 5 (4d), and M 4 , 5 (3d) edge photoelectron spectra were measured in an aqueous solution and computed using high-level multi-reference methods. Our previous publication mainly focused on obtaining reliable experimental evidence, whereas in the present article, we focused primarily on theoretical aspects. The complex electronic structure of I 3 − requires the inclusion of both static and dynamic correlation, e.g., via the multi-configurational perturbation theory treatment. However, the resulting photoelectron spectra appear to be very sensitive to problems with variational stability and intruder states. We attempted to obtain artifact-free spectra, allowing for a more reliable interpretation of experiments. Finally, we concluded that the 3d Photoelectron Spectrum (PES) is particularly informative, evidencing an almost linear structure with a smaller degree of bond asymmetry than previously reported. [ABSTRACT FROM AUTHOR]

A series of poly(2-hydroxyethyl methacrylate) (PHEMA) thin films entrapping photosensitizer Rose Bengal (RB) and tetrabutylammonium iodide (TBAI) have been synthetized. The materials have been characterized by means of Thermogravimetric Analysis (TGA), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) and UV-vis Absorption spectroscopy. Irradiation of the materials with white light led to the generation of several bactericidal species, including singlet oxygen (1O2), triiodide anion (I3−) and hydrogen peroxide (H2O2). 1O2 production was demonstrated spectroscopically by reaction with the chemical trap 2,2′-(anthracene-9,10-diylbis(methylene))dimalonic acid (ABDA). In addition, the reaction of iodide anion with 1O2 yielded I3− inside the polymeric matrix. This reaction is accompanied by the formation of H2O2, which diffuses out the polymeric matrix. Generation of both I3− and H2O2 was demonstrated spectroscopically (directly in the case of triiodide by the absorption at 360 nm and indirectly for H2O2 using the xylenol orange test). A series of photodynamic inactivation assays were conducted with the synthesized polymers against Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa. Complete eradication (7 log10 CFU/mL) of both bacteria occurred after only 5 min of white light irradiation (400–700 nm; total energy dose 24 J/cm2) of the polymer containing both RB and TBAI. The control polymer without embedded iodide (only RB) showed only marginal reductions of ca. 0.5 log10 CFU/mL. The main novelty of the present investigation is the generation of three bactericidal species (1O2, I3− and H2O2) at the same time using a single polymeric material containing all the elements needed to produce such a bactericidal cocktail, although the most relevant antimicrobial activity is shown by H2O2. This experimental approach avoids multistep protocols involving a final step of addition of I−, as described previously for other assays in solution. [ABSTRACT FROM AUTHOR]

Iodine is a broad-spectrum antiseptic with the advantage of not inducing bacterial resistance, but its use is limited by volatility. This issue can be overcome by using "iodophors", which are molecular systems able to retain iodine and provide its sustained release. Cyclodextrins have proven effective in stabilizing iodine in solution through the formation of complexes, the preparation of which in solid form could offer additional benefits in terms of handling and storage. A series of cyclodextrins (CD) were tested for their ability to form solid complexes with iodine and it was found that the addition of potassium iodide in the solid-state preparation of the complexes significantly increases both iodine incorporation and long-term stability compared to the solids obtained without added potassium iodide. Dilute aqueous solutions of the obtained complexes were monitored for their iodine content in different conditions and excellent stability was observed in some cases. Furthermore, these cyclodextrin‑iodine complexes showed no cytotoxic effects on human corneal epithelial cells (HCE-2) while displayed very high antimicrobial (against Staphylococcus epiderm is) and antiviral (against Human adenovirus 5) activities. These findings highlight the potential of cyclodextrins as a versatile platform for the development of solid iodophors as an alternative to the traditional povidone-iodide formulation. [Display omitted] [ABSTRACT FROM AUTHOR]

The I3− molecule is known to undergo substantial structural reorganization upon solvation by a protic solvent, e.g., water. However, the details of this process are still controversially discussed in the literature. In the present study, we combined experimental and theoretical efforts to disentangle this controversy. The valence (5p), N4,5 (4d), and M4,5 (3d) edge photoelectron spectra were measured in an aqueous solution and computed using high-level multi-reference methods. Our previous publication mainly focused on obtaining reliable experimental evidence, whereas in the present article, we focused primarily on theoretical aspects. The complex electronic structure of I3− requires the inclusion of both static and dynamic correlation, e.g., via the multi-configurational perturbation theory treatment. However, the resulting photoelectron spectra appear to be very sensitive to problems with variational stability and intruder states. We attempted to obtain artifact-free spectra, allowing for a more reliable interpretation of experiments. Finally, we concluded that the 3d Photoelectron Spectrum (PES) is particularly informative, evidencing an almost linear structure with a smaller degree of bond asymmetry than previously reported.

[Display omitted] • New data on the luminescence of EuX 2 (X = Cl, Br, I) in THF have been obtained. • The absence of absorption and PL of Eu2+ for a solution of EuI 2 in THF was found. • These negative effects are due to the triiodide impurity in EuI 2 -THF solution. • The addition of reducing agents to EuI 2 solution eliminates the triiodide effect. The photoluminescence (PL) spectra of solutions of commercial dihalides EuCl 2 (λ em = 417 nm) and EuBr 2 (λ em = 482 nm) in tetrahydrofuran C 4 H 8 O (THF), caused by emission from the excited state of the Eu2+* ion (transition 4f65d1 → 4f7), were measured for the first time. The red shift (65 nm) of the EuCl 2 PL band relative to the EuBr 2 band is attributed to the nephelauxetic effect. The PL quantum yields of EuCl 2 (φ = 0.07 %) and EuBr 2 (φ = 0.12 %), as well as the lifetimes of Eu2+* ions (194–213 ns) were determined. As a result of comparing the absorption spectrum of a solution of EuI 2 in THF with the absorption spectra of model THF solutions of iodide anion (NaI), molecular iodine (I 2) and triiodide ion (I 3 ¯) (NaI + I 2), it was discovered for the first time that commercial samples of EuI 2 contain an impurity of triiodide anion (I 3 ¯) in the form of europium triiodide Eu2+(I 3 ¯) 2 , the content of which, according to the results of iodometric titration, is 0.63 %. When EuI 2 is dissolved in THF, this impurity goes into solution and appears in the form of absorption bands at 295 and 366 nm and a weak "iodine" color. When this solution is exposed to metallic Eu or hydride iBu 2 AlH (iBu = iso -C 4 H 9), both triiodide bands at 295 and 366 nm and the "iodine" color disappear and the absorption band of the Eu2+ ion appears at 337 nm. The absorption spectra of THF solutions of EuCl 2 (λ abs = 248, 320 nm) and EuBr 2 (λ abs = 263, 394 nm), containing broad bands due to the 4f7 → 4f65d1 transition, were also measured. Unlike EuCl 2 and EuBr 2 , the Eu2+ maximum does not appear in the absorption spectrum of a solution of commercial EuI 2 in THF, because it is masked by the much stronger bands of the triiodide anion (I 3 ¯) at 295 and 366 nm. It has been established that PL of a solution of commercial EuI 2 in THF is not detected due to the quenching of its emitter Eu2+* by triiodide ion because of electron transfer from the excited Eu2+* ion to the triiodide anion with the formation of Eu3+ and iodide ion I¯. When metallic europium is added to a solution of commercial EuI 2 in THF, PL of the Eu2+ ion appears at 429 nm. This occurs as a result of the consumption of the PL quencher triiodide anion I 3 ¯ in the reaction with Eu to form iodide ion. A similar situation is observed when iBu 2 AlH is added to a solution of commercial EuI 2 in THF. [ABSTRACT FROM AUTHOR]

The interrelation between noncovalent bonds and physicochemical properties is in the spotlight due to the practical aspects in the field of crystalline material design. Such study requires a number of similar substances in order to reveal the effect of structural features on observed properties. For this reason, we analyzed a series of three substituted thiazolo[2,3-b][1,3]thiazinium triiodides synthesized by an iodocyclization reaction. They have been characterized with the use of X-ray diffraction, Raman spectroscopy, and thermal analysis. Various types of noncovalent interactions have been considered, and an S…I chalcogen bond type has been confirmed using the electronic criterion based on the calculated electron density and electrostatic potential. The involvement of triiodide anions in the I…I halogen and S…I chalcogen bonding is reflected in the Raman spectroscopic properties of the I−I bonds: identical bond lengths demonstrate different wave numbers of symmetric triiodide vibration and different values of electron density at bond critical points. Chalcogen and halogen bonds formed by the terminal iodine atom of triiodide anion and numerous cation…cation pairwise interactions can serve as one of the reasons for increased thermal stability and retention of iodine in the melt under heating.

[Display omitted] • Alkylpyrazolium iodides and alkylpyrazolium triiodides ionic liquids synthesis and characterization were reported. • Iodide and triiodide anions have a pronounced effect on the physicochemical and transport properties. • The triiodide anion has non-polar nature due to the larger volume for charge delocalization compared to iodide. • The alkylpyrazolium triiodides demonstrated high thermal stability, low viscosity, and high ionic conductivity. Ionic liquids (ILs) particularly imidazolium-based ILs have been widely used in various industrial applications such as solvent or catalyst for synthesis, as electrolyte in energy devices, and as solvent for extraction and separation. The extensive physical and chemical properties data available on the imidazolium-based ILs have made them easier to be incorporated into variety of applications compared to other types of ionic liquids. Ionic liquids composed of pyrazolium derivative as cation having the same heteroaromatic ring structure with imidazolium derivative except for the position of the nitrogen atoms, may result in unique physical and chemical properties, yet have been minimally explored. The main objective of this study is to investigate the physicochemical and transport properties of pyrazolium-based ILs to fully comprehend their potential for further development for a specific task or application. In this study, three alkylpyrazolium iodides ILs as well as corresponding three alkylpyrazolium triiodides ILs were synthesized and characterized. The NMR analysis showed that the formation of alkylpyrazolium triiodides ILs from their respective iodide precursors has resulted the resonance to be more deshielded due to lesser electron density experienced by the acidic protons of pyrazolium cation due to the weakly localized charge in triiodide anion. The effect of different anions and the alkyl chain of the pyrazolium cation moiety has a pronounced effect on the physical and transport properties of the synthesized ILs. It is found that the pyrazolium ionic liquids with triiodide anion demonstrated high thermal stability, low viscosity, and high ionic conductivity as compared to the iodide analogues. [ABSTRACT FROM AUTHOR]

The interrelation between noncovalent bonds and physicochemical properties is in the spotlight due to the practical aspects in the field of crystalline material design. Such study requires a number of similar substances in order to reveal the effect of structural features on observed properties. For this reason, we analyzed a series of three substituted thiazolo[2,3-b][1,3]thiazinium triiodides synthesized by an iodocyclization reaction. They have been characterized with the use of X-ray diffraction, Raman spectroscopy, and thermal analysis. Various types of noncovalent interactions have been considered, and an S...I chalcogen bond type has been confirmed using the electronic criterion based on the calculated electron density and electrostatic potential. The involvement of triiodide anions in the I...I halogen and S...I chalcogen bonding is reflected in the Raman spectroscopic properties of the I–I bonds: identical bond lengths demonstrate different wave numbers of symmetric triiodide vibration and different values of electron density at bond critical points. Chalcogen and halogen bonds formed by the terminal iodine atom of triiodide anion and numerous cation...cation pairwise interactions can serve as one of the reasons for increased thermal stability and retention of iodine in the melt under heating. [ABSTRACT FROM AUTHOR]