12-membered Ring Research Articles

Microwave-assisted rapid synthesis of nanosized SSZ-13 zeolites for effective conversion of ethylene to propylene

SSZ-13 is an attractive zeolite with chabazite topology composed of small pores with 8-membered rings. In this work, we report a highly effective method to synthesize SSZ-13s with microwave (MW) heating. Compared with conventional electric (CE) heating, MW heating accelerates both the nucleation and crystal growth rates of the synthesis by 6 and 18 times, respectively. Importantly, MW-assisted rapid synthesis produces the SSZ-13 with the smallest particles (<50 nm). However, the CE-assisted synthesis produces large/inhomogeneous particles (size: 0.4–1 μm). The obtained SSZ-13s were employed in acid catalysis or ethylene-to-propylene (ETP) reactions. The record-small SSZ-13s were more efficient in the ETP reactions, with more stable ethylene conversion/propylene yield (at the same time on stream) and higher propylene selectivity (at the same ethylene conversion), than large SSZ-13s. Finally, the maximum propylene yield (62%) is competitive or better than any SSZ-13s obtained via direct synthesis from precursors like silica and alumina.

Two Carboxylate-Cyanurates with Strong Optical Anisotropy and Large Band Gaps.

The first metal carboxylate-cyanurates, namely, K(H3C3N3O3)(HCO2) (I) and Ba2(H2C3N3O3)(CH3CO2)3(H2O) (II), which contain π-conjugated carboxylate and cyanurate groups, have been synthesized by hydrothermal methods. They crystallize in centrosymmetric space groups of P1̅ and P21/n, respectively. Compound I exhibits a novel three-dimensional (3D) structure based on a [K(H3C3N3O3)]+ cationic framework with 12-membered ring (12-MR) channels, and the (HCO2)- anions are located within the 12-MR channels. The [K(H3C3N3O3)]+ cationic framework is composed of K+ ions interconnected by H3C3N3O3 ligands. Compound II features a 3D network formed by [Ba2(CH3CO2)3]+ cationic double chains bridged by (H2C3N3O3)- anions. The [Ba2(CH3CO2)3]+ cationic double chain is composed of (CH3CO2)- anions and Ba2+ ions. Optical property measurements show that both compounds exhibit short ultraviolet cutoff edges (I, 208 nm; II, 218 nm) and wide band gaps (I, 5.43 eV; II, 5.20 eV). Importantly, K(H3C3N3O3)(HCO2) (I) features a large birefringence of 0.285@532 nm due to the parallel alignment of π-conjugated H3C3N3O3 and (HCO2)- groups, indicating that K(H3C3N3O3)(HCO2) (I) is a promising short-wave ultraviolet birefringent material. Detailed theoretical calculations elucidate that their excellent optical properties originate from the synergetic effect of both types of π-conjugated groups.

Improved catalytic performance in gas-phase dimethyl ether carbonylation over facile NH4F etched ferrierite.

Gas-phase dimethyl ether (DME) carbonylation to methyl acetate (MA) initiates a promising route for producing ethanol from syngas. Ferrierite (FER, ZSM-35) has received considerable attention as it displays excellent stability in the carbonylation reaction and its modification strategy is to improve its catalytic activity on the premise of maintaining its stability as much as possible. However, conventional post-treatment methods such as dealumination and desilication usually selectively remove framework Al or Si atoms, ultimately altering the intrinsic composition, crystallinity, and acidity of zeolites inevitably. In this study, we successfully prepared a series of hierarchical ZSM-35 materials through post-treatment with NH4F etching, which dissolved framework Al and Si at similar rates and preferentially attacked the defective sites. Interestingly, the produced pore systems effectively penetrated the [100] plane, offering elevated access to both the 8-membered ring (8-MR) and 10-membered ring (10-MR) channels. The physicochemical and acid properties of the pristine and NH4F etched ZSM-35 samples were comprehensively characterized using various techniques, including XRD, XRF, FESEM, HRTEM, Nitrogen adsorption-desorption, NH3-TPD, Py-IR, 27Al MAS NMR, and 29Si MAS NMR. Under moderate treatment conditions, the intrinsic microporous structure, acid properties, and crystallinity of zeolite were retained, leading to superior catalytic activity and stability with respect to the pristine sample. Nonetheless, severe NH4F etching disrupted the crystalline framework and created additional defective sites, bringing about faster deposition of coke precursors on the interior Brønsted acid sites (BAS) and decreased catalytic performance. This technique provides a novel and efficient method to slightly enhance the micropore and mesopore volume of industrially pertinent zeolites through a straightforward post-treatment, thus elevating the catalytic performance of these zeolites.

The crystal chemistry of plutonium(IV) borophosphate.

In this work, we report the synthesis and characterization of a plutonium(IV) borophosphate, Pu(H2O)3[B2(OH)(H2O)(PO4)3] (1). The basic building unit of 1 has a B : P ratio of 2 : 3 with an equal number of BO4 and PO4 groups that assemble into 12-membered rings and take on a sheet topology due to presence of hydroxyl groups or a water molecule on one vertex of each BO4 tetrahedron. This unique borophosphate anion topology is not observed in other members of the borophosphate family; it is the plutonium(IV) metal centers, rather than borate or phosphate groups, that link the sheets to form an extended framework. The presence of boron in 1 was confirmed using single crystal X-ray diffraction, electron microprobe analysis, and infrared spectroscopy. Peaks corresponding to the tetrahedral BO45- and tetrahedral PO43- anions were all identified in the fingerprint region (500-1500 cm-1) of the infrared spectrum. Additionally, peaks in the higher wavenumber region corresponded to crystalline water and B-OH vibrations, providing further evidence for the water molecules surrounding plutonium in the structure and the protonation of the BO4 tetrahedron, respectively. This compound represents the first Pu(IV) borophosphate structure and a novel borophosphate anion topology. Furthermore, the long time-frame required for crystallization of 1 and the suspected leaching of boron from the borosilicate vial used during synthesis indicate that 1 could serve as a model for the crystalline materials that are expected to form during the corrosion of vitrified nuclear waste.

Nitrogen rejection in natural gas using NaZSM-25 zeolite.

Natural gas reservoirs usually contain considerable amounts of nitrogen (N2). Methane (CH4) as the main component in natural gas must be purified before transferring to the pipeline or storing as liquified natural gas (LNG). Currently, energy-intensive cryogenic distillation is the only industrial approach for N2 rejection in natural gas. The adsorption process based on a N2-selective adsorbent can minimize the separation cost. However, the search for an adsorbent that can selectively reject N2 in natural gas has lasted for decades. Here, we report a microporous zeolite called NaZSM-25 capable of adsorbing N2 over CH4 with an exceptional selectivity of 47 at room temperature that outperforms all previously known N2-selective adsorbents. At 295 K and 100 kPa, the N2 and CH4 uptakes on NaZSM-25 were 0.25 and 0.005 mmol g-1, respectively. CH4 showed negligible external surface adsorption in the whole temperature range of 273-323 K. Theoretical studies through replica exchanged Monte Carlo, molecular dynamics, and ab initio density functional theory (DFT) proved the diffusion limitation of CH4 as a result of 8-membered ring (8MR) pore opening deformation by Na+ cation. The DFT results showed the diffusion energy barriers of 63 and 96 kJ mol-1 for N2 and CH4, respectively, when passing an 8MR occupied with a Na+. NaZSM-25 is a promising adsorbent to be utilized in a pressure swing adsorption process at room temperature to minimize the energy consumption in N2 rejection units.

Influence of an N,N,N-Trimethyl-1-adamantyl Ammonium (TMAda+) Structure Directing Agent on Al Distributions and Pair Features in Chabazite Zeolite

While organic structure directing agents (OSDAs) are well known to have a directional influence on the topology of a crystallizing zeolite, the relationship between OSDA charge and siting of aliovalent ions on a primarily siliceous framework is unclear. Here, we explore the relationship between OSDA orientation, Al3+ siting, and lattice energy, taking as a model system CHA zeolite occluded with N,N,N-trimethyl-1-adamantyl ammonium (TMAda+) at a Si/Al ratio of 11/1. We use density functional theory calculations to parametrize a fixed-charge classical model describing van der Waals and electrostatic interactions between the framework and OSDA. We enumerate and explore all possible combinations of OSDA orientation and Al location (attending to Löwenstein’s rule) within a 36 T-site supercell. We find that interaction energies vary over 60 kJ/double-six-ring-unit (d6r). Further, analysis of configurations reveals that energies are sensitive to Al–Al proximity, such that low energies are associated with Al3+ pairs in 8-membered rings and higher energies are associated with Al3+ pairs in smaller 6- and 4-membered rings. Comparisons with Al siting inferred from CHA zeolite crystallized with TMAda+ suggest that these computed interaction energies are useful reporters of observed Al siting in CHA synthesized with TMAda+.

Capture of novel sp hybridized Z-BN by compressing boron nitride nanotubes with small diameter

Experimental synthesis of new sp3 hybridized carbon/boron nitride structures remains challenging despite that numerous sp3 structures have been proposed in theory. Here, we showed that compressed multi-walled boron nitride nanotubes (MWBNNTs) and boron nitride peapods (C60@BNNTs) with small diameters could transform into a new sp3 hybridized boron nitride allotrope (Z-BN). This strategy is considered from the topological transition point of view in boron nitride nanotubes upon compression. Due to the increased curvature in compressed small-diameter MWBNNTs, the uncommon 4- and 8-membered rings in Z-BN could be more favorably formed. And the irreversible tube collapse is proved to be a critical factor for the capture of the formed Z-BN, because of the competition between the resilience of tube before collapse and the stress limitation for the lattice stabilization of Z-BN upon decompression. In this case, Z-BN starts to form above 19.0 GPa, which is fully reversible below 45 GPa and finally becomes quenchable at 93.5 GPa. This collapse-induced capture of the high-pressure phase could also be extended to other tubular materials for quenching novel sp3 structures.

Charge-separation driven mechanism via acylium ion intermediate migration during catalytic carbonylation in mordenite zeolite

By employing ab initio molecular dynamic simulations, solid-state NMR spectroscopy, and two-dimensional correlation analysis of rapid scan Fourier transform infrared spectroscopy data, a new pathway is proposed for the formation of methyl acetate (MA) via the acylium ion (i.e.,CH3 − C ≡ O+) in 12-membered ring (MR) channel of mordenite by an integrated reaction/diffusion kinetics model, and this route is kinetically and thermodynamically more favorable than the traditional viewpoint in 8MR channel. From perspective of the complete catalytic cycle, the separation of these two reaction zones, i.e., the C-C bond coupling in 8MR channel and MA formation in 12MR channel, effectively avoids aggregation of highly active acetyl species or ketene, thereby reducing undesired carbon deposit production. The synergistic effect of different channels appears to account for the high carbonylation activity in mordenite that has thus far not been fully explained, and this paradigm may rationalize the observed catalytic activity of other reactions.

DFT investigation of Li storage behavior of sceamless α-graphyne and β-graphyne nanotubes

Graphynes have great potential -as anode materials for lithium-ion batteries (LIBs) owing to their advanced structural and electronic properties. Previously, the curvature of γ-graphyne folded into nanotubes (γGyNTs) caused a significant increase in its Li storage capacity and diffusion ability. Here, using density functional theory (DFT) calculations, we report the same curvature effect in α- and β-graphyne nanotubes (αGyNTs and βGyNTs), whose maximum storage capacities are predicted to be -up to 3488 and 3070 mAh/g, respectively, similar to that of pure Li (3861 mAh/g). Such high capacities are attributed to the graphyne nanotubes having larger specific surface areas and pores than those of other carbon materials. Additionally, climbing -image- nudged-elastic- band calculations reveal that Li atoms can diffuse almost freely through acetylenic rings on the concave side of the αGyNTs, indicating an excellent charge -discharge rate ascribed to weaker adsorption on the 18-membered ring than that on the 12-membered rings of the βGyNTs and γGyNTs. Our results suggest that the αGyNTs are promising as the anode material for LIBs with exceptional overall performance. This study also provides a strategy to design anode materials based on their curvature and topological morphology.

Palladium-Catalyzed C-H Activation/Cyclization for the Synthesis of [60]Fullerene-Fused Phosphinolactones.

A novel and efficient palladium-catalyzed C-H activation reaction of [60]fullerene with arylphosphinic acids has been developed for the synthesis of [60]fullerene-fused phosphinolactones. A possible reaction mechanism is proposed to explain the generation of the obtained products. A representative product can be further electrochemically transformed into bis-benzylated 1,2- and 1,4-adducts of [60]fullerene. In addition, a [60]fullerene-fused phosphinolactone with a 12-membered ring can also be synthesized from the electrochemical ring expansion of the employed phosphinolactone with a 6-memebered ring with 1,2-bis(bromomethyl)benzene.

Comparison of Dimethyl Ether Carbonylation Performance over Some Zeolites Containing 8-Member Ring Pores

Comparison of Dimethyl Ether Carbonylation Performance over Some Zeolites Containing 8-Member Ring Pores

A computational insight into the intrinsic, Si-decorated and vacancy-defected γ-graphyne nanoribbon towards adsorption of CO2 and O2 molecules

In this study, the effects of decorating a silicon (Si) atom and applying a single vacancy defect on an armchair γ-graphyne nanoribbon (A-γ-GyNR) are investigated toward CO2 and O2 molecules adsorption. The magnetic and electronic transport properties, including the calculation of adsorption energy, charge transfer, magnetic moment, band structure, phonon dispersion and density of state (DOS), have been studied using the spin-polarized density functional theory (DFT) method. The stability of the proposed substrates is measured and different positions for gas molecules are considered. The results reveal that the highest amounts of adsorption energy of CO2 (0.63 eV) and O2 (2.2 eV) molecules belong to the substrate decorated with the Si atom in the 12-membered ring (H1) and acetylene linkage (B3), respectively. In addition, the removal of a carbon atom with sp hybridization improves the O2 molecule adsorption by 3.34 times compared to the primary substrate (P-GyNR). According to the recovery time calculations, the most appropriate desorption time is related to T1-M1 model. The current–voltage characteristic confirms that the resistance of the introduced sensors fully changed after sensing. This work can be considered as an effective step toward understanding and developing A-γ-GyNR-based gas sensors.

Ba6Zn6(B3O6)6(B6O12): Barium Zinc Borate Contains π-Conjugated [B3O6]3- Anions and [B6O12]6- Anion with Edge-Sharing BO4 Tetrahedra.

A novel barium zinc borate contains π-conjugated [B3O6]3- anions and [B6O12]6- anion with edge-sharing BO4 tetrahedra, Ba6Zn6(B3O6)6(B6O12), has been successfully synthesized via a high-temperature solution reaction. In its structure, the isolated planar π-conjugated B3O6 groups are interconnected by ZnO4 tetrahedra via corner sharing to construct a [Zn3(B3O6)3]3- single layer parallel to the ab plane with the large Zn3B6 9-member rings. Two adjacent [Zn3(B3O6)3]3- single layers are interconnected by [B6O12]6- anions into a two-dimensional [Zn6(B3O6)6(B6O12)]12- double layer with 1D tunnels of Zn4B8 12-member rings along the a-axis. Neighboring such double layers are packed in an A-B-A-B... fashion along the c axis, and the Ba2+ ions act as counterbalance cations filling in the voids of double layers. All of the planar π-conjugated [B3O6]3- groups in Ba6Zn6(B3O6)6(B6O12) are in approximately parallel arrangement, producing large optical anisotropy and birefringence. The UV-vis-NIR absorption spectrum manifests that the UV cutoff edge for the title compound is below 200 nm. Ba6Zn6(B3O6)6(B6O12) possesses the largest birefringence (0.115@1064 nm) among the zincoborates reported. Its thermal stability, infrared spectrum, and theoretical calculations were also performed.

Loomisite, Ba[Be2P2O8]⋅H2O, the first natural example with the zeolite ABW-type framework, from Keystone, Pennington County, South Dakota, USA

AbstractA new beryllophosphate mineral species, loomisite (IMA2022-003), ideally Ba[Be2P2O8]⋅H2O, was found from the Big Chief mine near Keystone, Pennington County, South Dakota, USA. It occurs as divergent sprays of very thin bladed crystals with a tapered termination. Individual crystals are found up to 0.80 × 0.06 × 0.03 mm. Associated minerals include dondoellite, earlshannonite, mitridatite, rockbridgeite, jahnsite-(CaMnFe) and quartz. No twinning or parting is observed macroscopically. Loomisite is murky white in transmitted light, transparent with white streak and silky to vitreous lustre. It is brittle and has a Mohs hardness of 3½–4, with perfect cleavage on {100} and {$\bar{1}$10}. The measured and calculated densities are 3.46(5) and 3.512 g/cm3, respectively. Optically, loomisite is biaxial (+), with α = 1.579(5), β = 1.591(5), γ = 1.606(5) (white light), 2V (meas.) = 82(2)° and 2V (calc.) = 85°. It is non-pleochroic under polarised light, with a very weak (r &gt; v) dispersion. The mineral is insoluble in water or hydrochloric acid. An electron microprobe analysis, along with the BeO content measured with an ICP-MS, yields an empirical formula (based on 9 O apfu) (Ba0.96Ca0.06)Σ1.02[(Be1.96Fe0.06)Σ2.02P1.99O8]⋅H2O, which can be simplified to (Ba,Ca)[(Be,Fe)2P2O8]⋅H2O.Loomisite is monoclinic, with space group Pn and unit-cell parameters a = 7.6292(18), b = 9.429(2), c = 4.7621(11) Å, β = 91.272(5)°, V= 342.47(14) Å3 and Z = 2. Its crystal structure is characterised by a framework of corner-sharing PO4 and BeO4 tetrahedra. The framework can be considered as built from the stacking of sheets consisting of 4- and 8-membered rings (4.82 nets) along [001] or hexagonal layers (63 nets) along [010]. The extra-framework Ba2+ and H2O are situated in the channels formed by the 8-membered rings. Topologically, loomisite represents the first natural example with the zeolite ABW-type framework, which is adopted by over 100 synthetic compounds with different chemical compositions.

Hydrogen Bonding Drives Helical Chirality via 10-Membered Rings in Dipeptide Conjugates of Ferrocene-1,1'-Diamine.

Considering the enormous importance of protein turns as participants in various biological events, such as protein–protein interactions, great efforts have been made to develop their conformationally and proteolytically stable mimetics. Ferrocene-1,1′-diamine was previously shown to nucleate the stable turn structures in peptides prepared by conjugation with Ala (III) and Ala–Pro (VI). Here, we prepared the homochiral conjugates of ferrocene-1,1′-diamine with l-/d-Phe (32/35), l-/d-Val (33/36), and l-/d-Leu (34/37) to investigate (1) whether the organometallic template induces the turn structure upon conjugation with amino acids, and (2) whether the bulky or branched side chains of Phe, Val, and Leu affect hydrogen bonding. Detailed spectroscopic (IR, NMR, CD), X-ray, and DFT studies revealed the presence of two simultaneous 10-membered interstrand hydrogen bonds, i.e., two simultaneous β-turns in goal compounds. A preliminary biological evaluation of d-Leu conjugate 37 showed its modest potential to induce cell cycle arrest in the G0/G1 phase in the HeLa cell line but these results need further investigation.

Aza-PNA: Engineering E-Rotamer Selectivity Directed by Intramolecular H-bonding.

The replacement of α(CH2) by NH in monomers of standard aeg PNA and its homologue β-ala PNA leads to respective aza-PNA monomers (1 and 2) in which the NαH can form either an 8-membered H-bonded ring with folding of the backbone (DMSO and water) or a 5-membered NαH─αCO (water) to stabilize E-type rotamers. Such aza-PNA oligomers with exclusive E rotamers and intraresidue backbone H-bonding can modulate its DNA/RNA binding and assembling properties.

Thermal stability and melting mechanism of diamond nanothreads: Insight from molecular dynamics simulation

In recent years, diamond nanothreads (DNTs) have attracted a wide attention of many experimental and theoretical studies. DNTs are composed of carbon polygons such as 5-, 6-, 7-, and 8-membered carbon rings. In this study, via molecular dynamics simulation we have studied the thermal stability and melting process of 15 lowest-energy DNTs into three classes; achiral, stiff-chiral, and soft-chiral, respectively. The achiral, stiff-chiral, and soft-chiral classes consist of 6, 4, and 5 molecular models, respectively. The results showed that DNTs have different melting points due to the various morphologies and different arrangements of carbon rings. Also, results showed that DNTs composed of purely 6-membered carbon rings have high thermal stability and melting point, wheras DNTs with dissimilar and distorted carbon polygons have lower melting point. In addition, the results showed that DNTs with Stone-Wales defects (SW) have lower thermal stability and melting point. Moreover, the results showed that the achiral, stiff-chiral, and soft-chiral DNTs have the same melting mechanism. During melting process, the increasing sp3 C-C bonds length and their dissociation occurs as the themperature increases. The broken bonds resulting in the formation of larger sp2-carbon rings. The higher temperatures lead to the dissociation of formed large rings and the formation of polyethylene-like molecular chains. Finally, at the melting point or after the melting point, these chains dissociate and the DNTs break down. In this study, the melting point of nanoparticles supported on 15 DNT substrates was also investigated via molecular dynamics simulation. The results showed that all DNTs increase the thermal stability and melting point of the nanoparticles. The role of DNTs in increasing the melting point obey the following trend: soft-chiarl > achiral > stiff-chiral. Soft-chiarl-DNTs with their helical morphologies show lowest deformation in the nanoparticle structure during the melting process.

Preparation of shaped binderless mordenite catalysts with controllable crystal sizes and their carbonylation performance

A series of shaped binderless mordenite (MOR) zeolites were prepared through hydrothermal transformation with commercial MOR zeolite as seeds and aluminosilicate as raw materials. To investigate the effect of alkalinity on the crystallization process, samples with different Na2O/SiO2 ratios from 0.041 to 0.12 were synthesized and characterized by XRD, SEM, N2 adsorption-desorption, NH3-TPD, ICP-OES and pyridine adsorption-infrared measurements. It was surprisingly found that alkalinity plays a pivotal role in the formation of the binderless MOR zeolites. At Na2O/SiO2 of 0.041, MOR zeolite could not be formed. Slightly increasing the Na2O/SiO2 to 0.043 and upwards, the binderless MOR zeolite was formed. XRD patterns and SEM images revealed that the primary MOR zeolite particle size increased from 104 nm to 266 nm with the Na2O/SiO2 ratio increasing from 0.043 to 0.10. Further increasing Na2O/SiO2 ratio to 0.12 led to the formation of 0.6–1.6 μm micro-sized crystals. NH3-TPD and pyridine-adsorbed IR results indicated that the amount and strength of Brønsted acid sites in 8-membered ring channel (8-MR) decreased with the Na2O/SiO2 ratio increasing to up to 0.10. Superior catalytic performance in dimethyl ether carbonylation was observed on the catalyst with a Na2O/SiO2 ratio of 0.043, which exhibited the shortest diffusion path and highest 8-MR Brønsted acid amounts. This work provides a practical way of preparing and optimizing shaped binderless zeolites.

Identification of polyketide synthase genes required for aspinolide biosynthesis in Trichoderma arundinaceum

The fungus Trichoderma arundinaceum exhibits biological control activity against crop diseases caused by other fungi. Two mechanisms that likely contribute to this activity are upregulation of plant defenses and production of two types of antifungal secondary metabolites: the sesquiterpenoid harzianum A (HA) and the polyketide-derived aspinolides. The goal of the current study was to identify aspinolide biosynthetic genes as part of an effort to understand how these metabolites contribute to the biological control activity of T. arundinaceum. Comparative genomics identified two polyketide synthase genes (asp1 and asp2) that occur in T. arundinaceum and Aspergillus ochraceus, which also produces aspinolides. Gene deletion and biochemical analyses in T. arundinaceum indicated that both genes are required for aspinolide production: asp2 for formation of a 10-member lactone ring and asp1 for formation of a butenoyl subsituent at position 8 of the lactone ring. Gene expression and comparative genomics analyses indicated that asp1 and asp2 are located within a gene cluster that occurs in both T. arundinaceum and A. ochraceus. A survey of genome sequences representing 35 phylogenetically diverse Trichoderma species revealed that intact homologs of the cluster occurred in only two other species, which also produced aspinolides. An asp2 mutant inhibited fungal growth more than the wild type, but an asp1 mutant did not, and the greater inhibition by the asp2 mutant coincided with increased HA production. These findings indicate that asp1 and asp2 are aspinolide biosynthetic genes and that loss of either aspinolide or HA production in T. arundinaceum can be accompanied by increased production of the other metabolite(s).Key points• Two polyketide synthase genes are required for aspinolide biosynthesis.• Blocking aspinolide production increases production of the terpenoid harzianum A.• Aspinolides and harzianum A act redundantly in antibiosis of T. arundinaceum.

Theoretical SERS study of the strength and suitability of Cu12 nanostar for SERS: Complete theoretical studies, coinage metal SM12 comparisons, benzothiazole (BTH) adsorbent

Theoretical calculations were used to optimize molecular structures which help determine binding energies, and elucidate electronic properties of unsubstituted benzothiazole (BTH) adsorption on metal star models, SM12 (M = Ag/Au/Cu). BTH tends to connect via its donor nitrogen and sulfur heteroatoms as well as the π-conjugated carbon atoms; adsorption is onto the bare metal atoms of the nanostar, a single 12-membered ring, involving increasingly stable adsorption energies of −3.25/-5.71/-17.57 kcal mol−1 for BTH-Ag12/Au12/Cu12 complexes as one ascends the Group 11 triad. From the electrophilicity values, it is clear that the outermost electrons of the system will be able to travel (injected) from the chemically adsorbed BTH unit into the adsorbent SM12 within the structure of the complex. The values for changes in enthalpy and entropy for all complexes studied herein show that the motion of the atoms is constrained due to the presence of the BTH; the adsorption of BTH onto the investigated SM12 adsorbents is spontaneous. The increase of dipole moments for the complexes in aqueous media support potential for molecular recognition; drug delivery-oriented applications of the complexes are predicted to undergo dissolution in polar media such as water, offering the possibility for drug molecule recognition applications. Raman inactive modes of BTH become active within the BTH-metal complexes and experience enhancement in intensity. Adsorption behavior and thermodynamics parameters also indicate that the Cu12 cluster has the strongest interaction with maximum adsorption energy of −17.6 kcal mol−1. Density of states spectral analysis supports the charge transfer, adsorption behavior, and other thermodynamic parameters. In conclusion, density functional theory (DFT) has helped to determine electronic characteristics of SM12 clusters which have been demonstrated to be highly sensitive to the presence of BTH; these findings can allow for the molecular pairs to be used in (bio) sensor devices and to potentially trace the drug in the human body via spectrophotometry.