Chemistry
Latest Publications


TOTAL DOCUMENTS

151
(FIVE YEARS 151)

H-INDEX

3
(FIVE YEARS 3)

Published By Mdpi Ag

2624-8549
Updated Saturday, 25 September 2021

Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 1089-1100
Author(s):  
Gerardo Concilio ◽  
Carmine Gaeta ◽  
Paolo Della Della Sala ◽  
Veronica Iuliano ◽  
Carmen Talotta ◽  
...  

Hexamethoxycalix[6]arene 3 forms a directional pseudorotaxane complex with the chiral axle (S)-(α-methyl-benzyl)benzylammonium 2+. Between the two (endo-chiral)[email protected] and (exo-chiral)[email protected] pseudorotaxane stereoisomers, the former is preferentially formed. This result confirms the validity of the “endo-α-methyl-benzyl rule”, previously reported by us. DFT calculations suggest that C-H···π interactions between the methyl group of 2+ and the calixarene aromatic rings, determine the stereoselectivity of the threading process toward the “endo-α-methyl-benzyl preference”. An amplification of optical rotation is observed upon formation of the pseudorotaxane complex (endo-chiral)[email protected] with respect to free axle 2+. Thus, the specifical rotation of the 1:1 mixture of chiral 2+∙B(ArF)4− salt and achiral 3 was augmented upon formation of the pseudorotaxane and DFT calculations were used to rationalize this result.


Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 1074-1088
Author(s):  
Nicola Coscia ◽  
Antonietta Cozzolino ◽  
Manohar Golla ◽  
Paola Rizzo

PPO co-crystalline (CC) films including azobenzene guest molecules have been prepared and characterized by WAXD, FTIR and UV-Visible measurements. Isomerization reactions of azobenzene (photo-induced trans to cis and spontaneous cis to trans) included in α and β nanoporous-crystalline (NC) phases leading to CC phases, or simply absorbed in amorphous phase have been studied on thick and thin films. Spectroscopic analysis shows that photo-isomerization of azobenzene occurs without expulsion of azobenzene guest molecules from crystalline phases. Sorption studies of α and β NC films immersed into photo-isomerized azobenzene solution reveal a higher selectivity of the β NC phase toward cis azobenzene isomer than the α NC phase, inducing us to propose the β NC phase as particularly suitable for absorbing spherically bulky guest molecules.


Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 1063-1073
Author(s):  
Slađana Đorđević ◽  
Slavko Radenković

Magnetically induced current densities, calculated at the M06-2X/def2-TZVP level using the diamagnetic-zero version of the continuous transformation of origin of current density (CTOCD-DZ) method, were employed to study the aromaticity in Li3B2− and Li4B2. It was found that the Li3/Li4 rings in Li3B2− and Li4B2 remarkably resemble the monocyclic Li3+ and Li42+ clusters. Unlike the parent Li3+ and Li42+ systems that sustain negligibly weak global current density circulation, the Li3B2− and Li4B2 clusters exhibit a strong diatropic current density. The present work demonstrates how structural modifications introduced by the B2 unit can be used for modulating the current density in cyclic Li-based clusters.


Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 1057-1062
Author(s):  
Teng Zhang ◽  
Cesare Grazioli ◽  
Huixia Yang ◽  
Kaiyue Jiang ◽  
Iulia Emilia Brumboiu ◽  
...  

The bottom-up synthesis and preliminary characterizations of a new biphenylene-based 2D framework are presented. This new low-dimensional carbon allotrope potentially completes the many hypothesized carbon networks based on biphenylene.


Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 1047-1056
Author(s):  
James A. H. Inkster ◽  
Anna W. Sromek ◽  
Vamsidhar Akurathi ◽  
John L. Neumeyer ◽  
Alan B. Packard

The dopamine D2 agonist MCL-524 is selective for the D2 receptor in the high-affinity state (D2high), and, therefore, the PET analogue, [18F]MCL-524, may facilitate the elucidation of the role of D2high in disorders such as schizophrenia. However, the previously reported synthesis of [18F]MCL-524 proved difficult to replicate and was lacking experimental details. We therefore developed a new synthesis of [18F]MCL-524 using a “non-anhydrous, minimally basic” (NAMB) approach. In this method, [18F]F− is eluted from a small (10–12 mg) trap-and-release column with tetraethylammonium tosylate (2.37 mg) in 7:3 MeCN:H2O (0.1 mL), rather than the basic carbonate or bicarbonate solution that is most often used for [18F]F− recovery. The tosylated precursor (1 mg) in 0.9 mL anhydrous acetonitrile was added directly to the eluate, without azeotropic drying, and the solution was heated (150 °C/15 min). The catechol was then deprotected with the Lewis acid In(OTf)3 (10 equiv.; 150 °C/20 min). In contrast to deprotection with protic acids, Lewis-acid-based deprotection facilitated the efficient removal of byproducts by HPLC and eliminated the need for SPE extraction prior to HPLC purification. Using the NAMB approach, [18F]MCL-524 was obtained in 5–9% RCY (decay-corrected, n = 3), confirming the utility of this improved method for the multistep synthesis of [18F]MCL-524 and suggesting that it may applicable to the synthesis of other 18F-labeled radiotracers.


Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 1037-1046
Author(s):  
Lohona K. Soro ◽  
Cyrille Charpentier ◽  
Frédéric Przybilla ◽  
Yves Mély ◽  
Aline M. Nonat ◽  
...  

The podand-type ligand L, based on a tertiary amine substituted by three pyridyl-6-phosphonic acid functions, forms hydrated complexes with Ln3+ cations. The luminescence properties of the YbL complex were studied in D2O as a function of the pD and temperature. In basic conditions, increases in the luminescence quantum yield and the excited state lifetime of the Yb centered emission associated with the 2F5/2 → 2F7/2 transition were observed and attributed to a change in the hydration number from two water molecules in the first coordination sphere of Yb at acidic pH to a single one in basic conditions. Upon the addition of TbCl3 salts to a solution containing the YbL complex in D2O, heteropolynuclear Yb/Tb species formed, and excitation of the Yb at 980 nm resulted in the observation of the typical visible emission of Tb as a result of a cooperative upconversion (UC) photosensitization process. The UC was further evidenced by the quadratic dependence of the UC emission as a function of the laser power density.


Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 1005-1021
Author(s):  
Heike Fliegl ◽  
Maria Dimitrova ◽  
Raphael J. F. Berger ◽  
Dage Sundholm

A recently developed methodology for calculating, analyzing, and visualizing nuclear magnetic shielding densities is used for studying spatial contributions including ring-current contributions to 1H nuclear magnetic resonance (NMR) chemical shifts of aromatic and anti-aromatic free-base porphyrinoids. Our approach allows a visual inspection of the spatial origin of the positive (shielding) and negative (deshielding) contributions to the nuclear magnetic shielding constants. Diatropic and paratropic current-density fluxes yield both shielding and deshielding contributions implying that not merely the tropicity of the current density determines whether the contribution has a shielding or deshielding character. Instead the shielding or deshielding contribution is determined by the direction of the current-density flux with respect to the studied nucleus.


Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 1022-1036
Author(s):  
Francesco Ferdinando Summa ◽  
Paolo Lazzeretti

It is shown that the electric dipole- and electric quadrupole–anapole polarizabilities, denoted respectively by fαβ′ and gα,βγ′, and the anapole magnetizability aαβ, are intrinsic properties of the electron cloud of molecules responding to optical fields. fαβ′ is a nonvanishing property of chiral and achiral compounds, whereas aαβ is suitable for enantiomer discrimination of chiral species. They can conveniently be evaluated by numerical integration, employing a formulation complementary to that provided by perturbation theory and relying on the preliminary computation of electronic current density tensors all over the molecular domain. The origin dependence of the dynamic anapolar response is rationalized via related computational techniques employing numerical integration, as well as definitions of molecular property tensors, for example, electric dipole and electric quadrupole polarizabilties and magnetizability. A preliminary application of the theory is reported for the Ra enantiomer of the hydrogen peroxide molecule, evaluating tensor components of electric dipole-anapole polarizability and anapole magnetizability as functions of the dihedral angle ϕ≡∠ H-O-O-H in the range 0∘≤ϕ≤180∘.


Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 979-990
Author(s):  
Nurhanan Murni Yunos ◽  
Sui Kiong Ling ◽  
Asiah Osman ◽  
Zunoliza Abdullah ◽  
Nor Jannah Sallehudin

This is the first report to identify the presence of 3-O-caffeoyl quinic acid (1), 4-O-caffeoyl quinic acid (2), 5-O-caffeoyl quinic acid (3), epi-catechin (4), and procyanidin B2 (5) in the young propagules of Rhizophora mucronata. Compounds 2–5 were purified and then treated against breast, colorectal, and ovarian cancer cell lines for 72 h and the results of the Sulphorhodomine-B (SRB) assay were evaluated for percent cell viability and IC50 values. Epi-catechin, 4-O-caffeoyl quinic acid, 5-O-caffeoyl quinic acid and procyanidin B2 showed strong to moderate inhibitory effects when treated on breast (T47D), colorectal (HT29), and ovarian (A2780, SKOV3) cancer cell lines with IC50 values ranging from 16.77 ± 0.58 to 28.28 ± 0.89 μg/mL. In silico evaluation was performed to evaluate the drug-likeness and toxicological effects of these compounds using Molinspiration calculation and OSIRIS program. It was found that compounds 2, 3, and 4 have the potential to be orally active and have a low risk in exerting the mutagenic, tumorigenic, irritant, and reproductive effects.


Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 991-1004
Author(s):  
Alessandro Landi ◽  
Francesco Ferdinando Summa ◽  
Guglielmo Monaco

The ascertainment of magnetic aromaticity is not necessarily straightforward, especially for large and bent systems, such as the cycloporphyrin nanorings recently synthesized by the group of Anderson. Six of these cycloporphyrin nanorings were studied here computationally. Indirect methods, based on nuclear shielding and magnetizabilities, and direct methods, based on standard quantum mechanics, were both used effectively to determine their magnetically induced current strength, which mostly confirmed Anderson’s classification. However, in the case of hexanions, and in particular for cyclohexaporphyrin hexacations, a significant cancellation of delocalized diatropic and paratropic flow occurred, showing that the resultant faint aromatic character was a result of competing aromatic and antiaromatic contributions, as also evidenced by the ipsocentric method. A warning is renewed on the use of isotropic shielding to determine the tropicity of the magnetically induced current.


Sign in / Sign up

Export Citation Format

Share Document