Water-Vapor Responsive Metallo-Peptide Nanofibers.

Short peptides are versatile molecules for the construction of supramolecular materials. Most reported peptide materials are hydrophobic, stiff, and show limited response to environmental conditions in the solid-state. Herein, we describe a design strategy for minimalistic supramolecular metallo-peptide nanofibers that, depending on their sequence, change stiffness, or reversibly assemble in the solid-state, in response to changes in relative humidity (RH).

In Silico Design and Characterization of a New Molecular Electride: Li@Calix[3]Pyrrole.

Electrides, in which anionic electrons are localized independently of the atoms in the compound, have shown promise, especially as catalysts and optoelectronic materials. Here, we present a new computationally designed molecular electride, Li@calix[3]pyrrole (Li@C3P). Electron density and electron localization function analyses unequivocally confirm the existence of localized electride electron density, outside the system, independent of any specific atoms.

Defect-Free Synthesis of a Fully π-Conjugated Helical Ladder Polymer and Resolution into a Pair of Enantiomeric Helical Ladders.

Fully π-conjugated ladder polymers with a spiral geometry represent a new class of helical polymers with great potential for organic nanodevices, but there is no precedent for an optically active helical ladder polymer totally composed of achiral units. We now report the defect-free synthesis and resolution of a fully π-conjugated helical ladder polymer with a rigid helical cavity, which has been achieved by quantitative and chemoselective acid-promoted alkyne benzannulations of a rationally designed, random-coil achiral polymer followed by chromatographic enantioseparation. Because of a sufficiently high helix-inversion barrier, the isolated excess one-handed helical ladder polymer with a degree of polymerization of more than 15 showed a strong circular dichroism with a dissymmetry factor of up to 1.

Chiral Calix[3]pyrrole Derivatives: Synthesis, Racemization Kinetics, and Ring Expansion to Calix[9]- and Calix[12]pyrrole Analogues.

Chiral pyrrolic macrocycles continue to attract interest. However, their molecular design remains challenging. Here, we report a calixpyrrole-based chiral macrocyclic system, calix[1]furan[1]pyrrole[1]thiophene (1), synthesized from an oligoketone.

One-Handed Helical Tubular Ladder Polymers for Chromatographic Enantioseparation.

Defect-free one-handed contracted helical tubular ladder polymers with a π-electron-rich cylindrical helical cavity were synthesized by alkyne benzannulations of the random-coil precursor polymers containing 6,6'-linked-1,1'-spirobiindane-7,7'-diol-based chiral monomer units. The resulting tightly-twisted helical tubular ladder polymers showed remarkably high enantioseparation abilities toward a variety of chiral hydrophobic aromatics with point, axial, and planar chiralities. The random-coil precursor polymer and analogous rigid-rod extended helical ribbon-like ladder polymer with no internal helical cavity exhibited no resolution abilities.

Molecular Electrides: An In Silico Perspective.

Electrides are defined as the ionic compounds where the electron(s) serves as an anion. These electron(s) is (are) not bound to any atoms, bonds, or molecules but are rather localized into the space, crystal voids, or interlayer between two molecular slabs. There are three major categories of electrides, known as organic electrides, inorganic electrides, and molecular electrides.

DNA-Mimicking Metal-Organic Frameworks with Accessible Adenine Faces for Complementary Base Pairing.

Biologically derived metal-organic frameworks (Bio-MOFs) are significant, as they can be used in cutting-edge biomedical applications such as targeted gene delivery. Herein, adenine (Ade) and unnatural amino acids coordinate with Zn to produce biocompatible frameworks, KBM-1 and KBM-2, with extremely defined porous channels. They feature an accessible Watson-Crick Ade face that is available for further hydrogen bonding and can load single-stranded DNA (ssDNA) with 13 and 41% efficiency for KBM-1 and KBM-2, respectively.

Intriguing structural, bonding and reactivity features in some beryllium containing complexes.

Although the toxicity of beryllium compounds causes impediments in experiments involving them, beryllium chemistry has seen a recent upsurge of interest and considerable progress. Computations play a very important complementary role in analyzing the structure, stability and bonding of these compounds. In this perspective article, we highlighted our contribution to beryllium chemistry which is either completely through theoretical results or sometimes supported by experimental findings.

Two Closely Related Zn(II)-MOFs for Their Large Difference in CO Uptake Capacities and Selective CO Sorption.

Two azo functionalized Zn(II)-based MOFs, {[Zn(SDB)(3,3'-L)]·G}, IITKGP-13A, and {[Zn(SDB)(4,4'-L)]·G}, IITKGP-13B (IITKGP stands for Indian Institute of Technology Kharagpur), have been constructed through the self-assembly of isomeric N,N'-donor spacers (3,3'-L = 3,3'-azobispyridine and 4,4'-L = 4,4'-azobispyridine) with organic ligand 4,4'-sulfonyldibenzoic acid (SDBH) and Zn(NO)·6HO (G represents disordered solvent molecules). Single-crystal X-ray diffraction studies reveal the 2D structure with topology for both MOFs. However, the subtle change in positions of coordinating N atoms of spacers makes IITKGP-13A noninterpenetrated, while IITKGP-13B bears a 2-fold interpenetrated structure.

Encapsulation of Mg inside a C cage forms an electride.

Density functional theory (DFT) based calculations have been carried out for the endohedral encapsulation of magnesium dimer inside fullerene, that is, Mg @C . It is observed that the minimum energy structure of the Mg @C system is C symmetry. The MgMg bond distance in the Mg @C system is much shorter than that in the free Mg and Mg ion.

Flexibility Induced Encapsulation of Ultrafine Palladium Nanoparticles into Organic Cages for Tsuji-Trost Allylation.

A series of three positional isomers of organic cages namely , , and , have been self-assembled using dynamic covalent chemistry. Their room temperature controlled fabrication with palladium gives ultrafine diameter (1-2 nm) of palladium nanoparticles (Pd NPs). We observed that the shape-flexibility of cages have great impact on the formation of Pd NPs.

Metal-Organic Frameworks of Cu(II) Constructed from Functionalized Ligands for High Capacity H and CO Gas Adsorption and Catalytic Studies.

Two Cu(II)-based metal-organic frameworks (MOFs) having paddle-wheel secondary building units (SBUs), namely, and , were synthesized solvothermally using two new bent di-isophthalate ligands incorporating different substituents. The MOFs showed high porosity (BET surface area, 2191 m/g for and 1402 m/g for ). For , very high CO adsorption (98.

Filling the void: controlled donor-acceptor interaction facilitates the formation of an M-M single bond in the zero oxidation state of M (M = Zn, Cd, Hg).

The intriguing question of whether it is possible to form a genuine M0-M0 single bond for the M2 species (M = Zn, Cd, Hg) is addressed here. So far, all the bonds reported in the literature are exclusively MI-MI. Herein, we present viable M2(NHBMe)2 (M = Zn, Cd, Hg; NHBMe = (HCNMe)2B) complexes in which the controlled donor-acceptor interaction leads to an M0-M0 single bond.

Activation of Small Molecules (H, CO, NO, CH, and CH) by a Porphyrinoid-Based Dimagnesium(I) Complex, an Electride.

A density functional theory-based computation has been carried out to reveal the geometrical and electronic structures of MgEP (), where EP is an extended (3.1.3.

Stabilization of Boron-Boron Triple Bonds by Mesoionic Carbenes.

Density functional theory-based computations are carried out to analyze the electronic structure and stability of B(MIC) complexes, where MIC is a mesoionic carbene, viz., imidazolin-4-ylidenes, pyrazolin-4-ylidene, 1,2,3-triazol-5-ylidene, tetrazol-5-ylidene, and isoxazol-4-ylidene. The structure, stability, and the nature of bonding of these complexes are further compared to those of the previously reported B(NHC) and B(cAAC).

How Far Can One Push the Noble Gases Towards Bonding?: A Personal Account.

Noble gases (Ngs) are the least reactive elements in the periodic table towards chemical bond formation when compared with other elements because of their completely filled valence electronic configuration. Very often, extreme conditions like low temperatures, high pressures and very reactive reagents are required for them to form meaningful chemical bonds with other elements. In this personal account, we summarize our works to date on Ng complexes where we attempted to theoretically predict viable Ng complexes having strong bonding to synthesize them under close to ambient conditions.

Unprecedented Bonding Situation in Viable E (NHB ) (E=Be, Mg; NHB =(HCN ) B) Complexes: Neutral E Forms a Single E-E Covalent Bond.

Is it possible to facilitate the formation of a genuine Be-Be or Mg-Mg single bond for the E species while it is in its neutral state? So far, (NHC )Be-Be(NHC ) (R=H, Me, Ph) have been reported where Be is in Δ excited state imposing a formal Be-Be bond order of two. Herein, we present the formation of a single E-E (E=Be, Mg) covalent bond in E (NHB ) (E=Be, Mg; NHB =(HCN ) B) complexes where E is in ∑ excited state having (nσ ) (nσ ) ((n+1)σ ) (n=2 for Be and n=4 for Mg) valence electron configuration and it forms electron-shared bonding with two NHB radicals. The effects of bonding with nσ and (n+1)σ orbitals will cancel each other, providing the former E-E bond order as one.

Boron Nanowheels with Axles Containing Noble Gas Atoms: Viable Noble Gas Bound M©B Clusters (M=Nb, Ta).

The viability of noble gas axled boron nanowheels Ng M©B (Ng=Ar-Rn; M=Nb, Ta; n=1, 2) is explored by ab initio computations. In the resulting Ng -M complexes, the Ng-M-Ng nanorod passes through the center of the B ring, providing them with an inverse sandwich-like structure. While in the singly Ng bound analogue, the Ng binding enthalpy H at 298 K ranges from 2.

A Cu(ii)-MOF capable of fixing CO from air and showing high capacity H and CO adsorption.

A porous Cu(ii)-MOF shows an adsorption of 6.6 wt% of H at 77 K and 62 bar and a very high 60 wt% of CO at 298 K and 32 bar. When air is bubbled into a suspension of the activated MOF in the presence of different epoxides at room temperature, the CO in air is readily converted into the corresponding cyclic carbonates.

NgMCp: Noble Gas Bound Half-Sandwich Complexes (Ng = He-Rn, M = Be-Ba, and Cp = η-CH).

Structures, bonding, and stability of half-sandwich complexes with general formula, NgMCp (Ng = He-Rn, M = Be-Ba, Cp = η-CH) are analyzed through ab initio computation. MCp complexes possess remarkable Ng binding ability, particularly for M = Be and Mg. While for Ar-Rn bound analogues the bond dissociation energy in the former complex ranges within 17.

A Spinning Umbrella: Carbon Monoxide and Dinitrogen Bound MB Clusters (M = Co, Rh, Ir).

Strong binding of carbon monoxide (CO) and dinitrogen (N) by MB (M = Co, Rh, Ir) clusters results in a spinning umbrella-like structure. For OCMB and NNMB complexes, the bond dissociation energy values range within 50.3-67.

Ligand-Supported E Clusters (E=Si-Sn).

The interaction among E (E=Si, Ge, Sn) clusters and different ligands (L) encompassing five carbon-based donors (cyclic (alkyl)(amino)carbene (cAAC), N-heterocyclic carbene (NHC), saturated NHC (SNHC), mesoionic carbenes (MIC1, and MIC2)), two nitrogen-based donors (trimethylamine and pyridine), and two phosphorous-based donors (phosphinine and trimethylphosphine) in E (L) complexes is explored through DFT computations. Although all carbenes form very strong bonds with E clusters, cAAC makes the strongest bond with Si and Ge clusters, and MIC1 with the Sn cluster. Nevertheless, other ligand-bound complexes are also viable at room temperature.

The strongest CO binding and the highest C-O stretching frequency.

A coupled-cluster study is performed on CO bound BeY complexes (Y = O, CO, SO, NH, NCN, and NBO) to understand the effect of attached ligands (Y) on the CO binding ability and C-O stretching frequency (ν). Herein, we report that BeNCN has the highest CO binding ability (via both C- and O-side binding) among the studied neutral Be-based clusters, whereas OCBeSO has the highest ν among the neutral carbonyls. The nature and extent of shift in ν compared to free CO are explained in terms of change in polarization in the bonding orbitals of CO and relative contribution from OC→BeY or CO→BeY σ-donation, and OC←BeY or CO←BeY π-back-donation.

Statistical Significance of the Maximum Hardness Principle Applied to Some Selected Chemical Reactions.

The validity of the maximum hardness principle (MHP) is tested in the cases of 50 chemical reactions, most of which are organic in nature and exhibit anomeric effect. To explore the effect of the level of theory on the validity of MHP in an exothermic reaction, B3LYP/6-311++G(2df,3pd) and LC-BLYP/6-311++G(2df,3pd) (def2-QZVP for iodine and mercury) levels are employed. Different approximations like the geometric mean of hardness and combined hardness are considered in case there are multiple reactants and/or products.

σ-Aromatic cyclic M3(+) (M = Cu, Ag, Au) clusters and their complexation with dimethyl imidazol-2-ylidene, pyridine, isoxazole, furan, noble gases and carbon monoxide.

The σ-aromaticity of M3(+) (M = Cu, Ag, Au) is analyzed and compared with that of Li3(+) and a prototype σ-aromatic system, H3(+). Ligands (L) like dimethyl imidazol-2-ylidene, pyridine, isoxazole and furan are employed to stabilize these monocationic M3(+) clusters. They all bind M3(+) with favorable interaction energy.