Substituent and Solvent Effects on the Absorption Spectra of Cation-π Complexes of Benzene and Borazine: A Theoretical Study

Cation-lone Pair Interaction in Alkali/Alkaline Earth Metal Ion-Heavier Borazine Analogue Complexes

The present study is the first report on the formation of alkali/alkaline earth metal ion-heavier borazine analogue complexes via cation-lone pair interaction. Density functional calculations are performed in scrutinizing the complex formation between alkali (Li+, Na+, K+)/alkaline earth (Be2+, Mg2+, Ca2+) metal ions and heavier borazine analogues (HBA) viz. B3P3H6, Al3N3H6, Al3P3H6, Al3As3H6, and Ga3P3H6. The complexes are found to be stable in gas phase with stabilization energies within the range 26.40-324.74 kcal mol-1. The stability can be attributed to the polarizing power of the involved metal ions. Presence of solvent phase exerted notable impact on the stability of the complexes; stability is reduced significantly with the increase in solvent polarity. The process of complexation is exothermic and spontaneous. QTAIM analysis indicated the presence of both ionic and covalent interaction between HBAs and metal ions. HOMO energy, Wiberg bond index, NCI-isosurface and RDG plot analysis revealed the major role of cation-lone pair interaction in the complexation process.

Exploring Coumarin-Based Boron Emissive Complexes as Temperature Thermometers in Polymer-Supported Materials

Three coumarin-based boron complexes (L1, L2 and L3) were designed and successfully incorporated into polymeric matrixes for evaluation as temperature probes. The photophysical properties of the complexes were carried out in different solvents and in the solid state. In solution, compound L1 exhibited the highest fluorescence quantum yield, 33%, with a positive solvatochromism also being observed on the absorption and emission when the polarity of the solvent increased. Additionally in the presence of anions, L1 showed a colour change from yellow to pink, followed by a quenching in the emission intensity, which is due to deprotonation with the formation of a quinone base. Absorption and fluorescence spectra of L1 were calculated at different temperatures by the DFT/B3LYP method. The decrease in fluorescence of compound L1 with an increase in temperature seems to be due to the presence of pronounced torsional vibrations of the donor and acceptor fragments relative to the single bond with C(carbonyl)-C (styrene fragment). L1, L2 and L3, through their incorporation into the polymeric matrixes, became highly emissive by aggregation. These dye@doped polymers were evaluated as temperature sensors, showing an excellent fluorescent response and reversibility after 15 cycles of heating and cooling.

Formation of sandwich and multidecker complexes between O2 and alkali/alkaline earth metals: A DFT study

Abstract: Feasibility of formation of sandwich and multidecker complexes between O2 molecules and alkali/alkaline earth metal has been analyzed in the light of density functional theory (DFT). High value of...

Superalkali-doped borazine and lithiated borazine complexes: diffuse excess electron and large first-hyperpolarizability

A number of superalkali (M₃O / M₃S; M = Li, Na, K)-doped borazine and hexalithio borazine complexes are considered for the theoretical study of their electronic structure and quadratic polarizability. Electron-rich O/S atom of superalkali species remains very close to one boron atom of the ring through non-covalent interaction. The first-hyperpolarizability increases rather significantly upon superalkali doping. The chosen complexes possess diffuse excess electron which is located on the superpalkali moiety of borazine complexes and at the ring site of lithiated borazines. First-hyperpolarizability of M₃O(S)@B₃N₃Li₆ complexes are significantly larger than that of the corresponding M₃O(S)@B₃N₃H₆ complexes. The magnitude of first-hyperpolarizability of Li₃S@B₃N₃Li₆ is larger than that of Li₃S@B₃N₃H₆ by about three orders of magnitude.

A theoretical investigation on the complexes of B3O3H3 with acetylene and its substituted derivatives

The complexes of B₃O₃H₃ with acetylene and its substituted derivatives C₂HX (X=H, F, Cl, Br, CH₃, NH₂) are explored by theoretical calculations using MP2 and M06-2X methods with aug-cc-pVDZ as the basis set. The different molecular electrostatic potential features of B₃O₃H₃ with benzene (C₆H₆) and borazine (B₃N₃H₆) result in different stable structures of the complexes with C₂HX. The geometric analysis indicates that the global minimum is the parallel stacked (PS) structure with the linear C-C triple bond lies on the top of B₃O₃H₃, and this is much different from that of the B₃N₃H₆...C₂HX complex, in which the C-H bond directs towards the B₃N₃H₆ ring (T-shaped). The H-bonded structure where the C-H interacts with the O atom of B₃O₃H₃ is found to be a local minimum. Besides, there is an additional X…O halogen-bonded structures for the B₃O₃H₃…C₂HX (X=Cl, Br) complexes. As for the PS geometry, when one H atom in C₂H₂ is replaced by different X groups, the binding energies of the complexes increases in the order of F<H<Cl<Br<CH₃<NH₂, which is mainly determined by the strength of the π-hole bond. The nature of interaction in these complexes is further studied by the atoms-in-molecules (AIM) and noncovalent interaction (NCI) analysis. The natural bond orbital (NBO) analysis indicates that the main orbital interaction arises from LP_X→BD*_B‑O for B₃O₃H₃…C₂HX (X=Cl, Br, NH₂), and BD_C‑C→BD*_B‑O for B₃O₃H₃…C₂HX (X=H, CH₃) complexes. Complexes of B₃O₃H₃ with acetylene and its substituted derivatives.

B-Hb⋯π interactions in benzene–borazine sandwich and multidecker complexes: a DFT study

Multidecker complexes of benzene/borazine can be formed through B-H_b⋯π interactions.

Association of phenyldiboronic acids with hydrogen bond acceptors to form hydrogen bonded DD·AA-type complexes: a DFT study

DD·AA-type complexes of phenyldiboronic acids.

B–Hb⋯π interaction in borane–graphene complexes: coronene as a case study

N/B/BN doping in graphene enhances adsorption of boranes.

Cation–π interaction in cofacial molecular dyads: a DFT and TDDFT study

Cation–π interaction in molecular tweezer.

A one-step route to solubilised, purified or functionalised single-walled carbon nanotubes

Reductive dissolution is a promising processing route for single walled carbon nanotubes (SWCNTs) that avoids the damage caused by ultrasonication and aggressive oxidation whilst simultaneously allowing access to a wealth of SWCNT functionalisation reactions. Here, reductive dissolution has been simplified to a single one-pot reaction through the use of sodium naphthalide in dimethylacetamide allowing direct synthesis of SWCNT Na+ solutions. Gram quantities of SWCNTs can be dissolved at concentrations over 2 mg mL-1. These reduced SWCNT solutions can easily be functionalised through the addition of alkyl halides; reducing steric bulk of the grafting moiety and increasing polarisability of the leaving group increases the extent of functionalisation. An optimised absolute sodium concentration of 25 mM is shown to be more important than carbon to metal ratio in determining the maximum degree of functionalisation. This novel dissolution system can be modified for use as a non-destructive purification route for raw SWCNT powder by adjusting the degree of charging to dissolve carbonaceous impurities, catalyst particles and defective material, before processing the remaining SWCNTs.

Rational design of a fluorescent poly(N-aryleneindole ether sulfone) switch by cation–π interactions

A fluorescence emission on–off switch is achieved by adjusting the assembly of poly(N-aryleneindole ether sulfone) (PESIN) and pyridine hydrochloride via the cation–π interactions.