Dimer Bond Research Articles

Sequential pretreatment with hydroxyl radical and manganese peroxidase for the efficient enzymatic saccharification of corn stover

BackgroundWhite rot fungi produce various reactive oxygen species and ligninolytic enzymes for lignocellulose deconstruction. However, their interactions during the deconstruction of lignocellulosic structural barriers for efficient enzymatic saccharification remain unclear.ResultsHerein, the extracellular enzyme activities and secretomic analysis revealed the sequential expression of hydroxyl radical (⋅OH) and manganese peroxidases (MnPs) for lignocellulose deconstruction by the white rot fungus Irpex lacteus. Subsequently, in vitro functional studies found that ⋅OH possessed the ability to disrupt the smooth surface structure of corn stover, resulting in increased enzymatic saccharification and cellulose accessibility. Purified recombinant MnPs from I. lacteus were able to cleave the β-O-4 bond in phenolic and non-phenolic lignin model dimers without the help of any mediators. Furthermore, the sequential pretreatment of corn stover with ⋅OH and MnP exhibited significant synergistic effects, increasing enzymatic saccharification and cellulose accessibility by 2.9-fold and 1.8-fold, respectively.ConclusionsThese results proved for the first time the synergistic effects of ⋅OH and MnP pretreatment in improving the enzymatic saccharification and cellulose accessibility of corn stover. These findings also demonstrated the potential application of ⋅OH and MnP pretreatment for the efficient enzymatic saccharification of corn stover.Graphical

Crystallization-Induced Dimerization and Solution-Phase Bond Dissociation of Stable Dibenzoolympicenyl Radicals.

Crystallization of organic materials can lead to different assembly structure with different reactivity, but this phenomenon is rarely observed for delocalized hydrocarbon radicals. This report introduces a crystallization-induced radical-radical coupling reaction, which employs a series of stable nonplanar organic π-radicals as reactants. Six stable radical congeners are synthesized, resulting in radical-radical coupling at the allenyl radical site during crystallization to produce close-shell dimers. This coupling reaction is absent in the solution phase, which highlights the importance of preorganization in the lattice. Remarkably, the attempts of cocrystallization of different congeners yielded homocoupling products instead of cross-coupling products. In specific cases, two distinct polymorphs are observed and their reactivity is different according to the distance of the reaction sites. Theoretical calculations indicate that the transition from a metastable preorganized monomer to a dimer is barrierless and spontaneous. The dimer could regenerate free radicals by heating or photoirradiation in the solution phase. This discovery may lead to controllable molecular switches.

An Engineered Laccase from Fomitiporia mediterranea Accelerates Lignocellulose Degradation.

Laccases from white-rot fungi catalyze lignin depolymerization, a critical first step to upgrading lignin to valuable biodiesel fuels and chemicals. In this study, a wildtype laccase from the basidiomycete Fomitiporia mediterranea (Fom_lac) and a variant engineered to have a carbohydrate-binding module (Fom_CBM) were studied for their ability to catalyze cleavage of β-O-4' ether and C-C bonds in phenolic and non-phenolic lignin dimers using a nanostructure-initiator mass spectrometry-based assay. Fom_lac and Fom_CBM catalyze β-O-4' ether and C-C bond breaking, with higher activity under acidic conditions (pH < 6). The potential of Fom_lac and Fom_CBM to enhance saccharification yields from untreated and ionic liquid pretreated pine was also investigated. Adding Fom_CBM to mixtures of cellulases and hemicellulases improved sugar yields by 140% on untreated pine and 32% on cholinium lysinate pretreated pine when compared to the inclusion of Fom_lac to the same mixtures. Adding either Fom_lac or Fom_CBM to mixtures of cellulases and hemicellulases effectively accelerates enzymatic hydrolysis, demonstrating its potential applications for lignocellulose valorization. We postulate that additional increases in sugar yields for the Fom_CBM enzyme mixtures were due to Fom_CBM being brought more proximal to lignin through binding to either cellulose or lignin itself.

Catalytic carbon–carbon bond cleavage in lignin via manganese–zirconium-mediated autoxidation

Efforts to produce aromatic monomers through catalytic lignin depolymerization have historically focused on aryl–ether bond cleavage. A large fraction of aromatic monomers in lignin, however, are linked by various carbon–carbon (C–C) bonds that are more challenging to cleave and limit the yields of aromatic monomers from lignin depolymerization. Here, we report a catalytic autoxidation method to cleave C–C bonds in lignin-derived dimers and oligomers from pine and poplar. The method uses manganese and zirconium salts as catalysts in acetic acid and produces aromatic carboxylic acids as primary products. The mixtures of the oxygenated monomers are efficiently converted to cis,cis-muconic acid in an engineered strain of Pseudomonas putida KT2440 that conducts aromatic O-demethylation reactions at the 4-position. This work demonstrates that autoxidation of lignin with Mn and Zr offers a catalytic strategy to increase the yield of valuable aromatic monomers from lignin.

Short chiral pitch and blue phase stability in cholesteric liquid crystal mixtures by adding achiral benzoic acid derivative

ABSTRACT Cholesteric liquid crystal (CLC) is anticipated to have applications such as blue light and ultraviolet (UV) light blocking for human skin owing to its selective wavelength reflection against incident sunlight through several hundred nanometres of a periodic helical twist structure. In this study, we investigated short chiral pitch control and enlargement of the blue phase (BP) temperature range by adding an achiral constituent of 4-n-octylbenzoic acid (8 BA) into CLC mixtures composed of three kinds of cholesteryl compounds: cholesteryl chloride, cholesteryl pelargonate and cholesteryl palmitate. Hydrogen bonding dependence of chiral pitch and BP temperature range were also investigated for achiral dopant (8 BA) and CLC mixture through temperature-dependent Fourier-transform infrared analysis. It was found that 40 wt% of 8 BA within the CLC mixture selectively reflected UV and blue light over 360–400 nm with a decrease of chiral pitch. It was also found that the BP temperature range increased by 15.6°C owing to hydrogen bond dimers composed of 8 BA molecules in the CLC mixture.

The inter-molecular hydrogen bonds modulated reversible ACQ-AIE conversion and dual-states sensing applications of shikimic acid derived hydrogen bond dimers

Smart molecules with adjustable and reversible ACQ-AIE transformation which could be used as luminescence sensors both in solvent and solid-state are rarely reported. Planar luminophores with strong inter-molecular hydrogen bonds and a rotor might exhibit reversible ACQ-AIE conversion by modulating the inter-molecular hydrogen bonds. As a proof of concept, herein, two smart hydrogen bond dimers (Qufu-1 and Qufu-2) with reversible ACQ-AIE transformation were derived from the renewable bio-feedstock shikimic acid. Qufu-1 and Qufu-2 possessing a novel 4-oxo-3,4-dihydrobenzofuro[2,3-d]pyrimidine key structure and both exhibit crystallization induced ACQ (CIACQ) and precipitation induced AIE (PIAIE) in solid-state. Single crystal analysis indicates that the large planar configuration formed in the dimers of Qufu-1 and Qufu-2 due to the inter-molecular hydrogen bonds, which would result in the strong π-π stacking and ACQ in crystal. The AIE state could be facile realized by breaking the inter-molecular hydrogen bonds and changing the aggregation state from crystal to precipitation. Moreover, ACQ to AIE transformation could also accomplish for Qufu-1 and Qufu-2 in solution by modulating the inter-molecular hydrogen bonds with acid. In addition, three-level structures latent fingerprint identification in real environment and fluorescent sensing of hazardous biogenic amines in food samples were performed with Qufu-1.

Potential energy surfaces of antiparallel water-water interactions

Antiparallel water-water interaction is a significant interaction between two water molecules and plays an important role in liquid water. The potential energy surface of antiparallel water-water interaction was calculated at accurate CCSD(T)/CBS level of theory by systematic changes of the torsion angle THOHO, parallel displacement r, normal distance R, and water-water dihedral angle Pa/Pb. The results show that the most stable geometry of antiparallel water-water interaction has an interaction energy of −4.22 kcal/mol and THOHO = 140°. A significant portion of the antiparallel interactions have interaction energies more negative than −2.0 kcal/mol. The angle α of the most stable geometries of antiparallel water-water interactions is in the range 110°–120°. Comparison with classical hydrogen bonds in water dimers shows that hydrogen bonds with values of angle α < 140° have interaction energies up to −3.2 kcal/mol, while a significant number of antiparallel water-water interactions is stronger than it. The antiparallel geometry is a low barrier transition state between two hydrogen bonded minima with changed acceptor–donor roles of two water molecules.

Two-dimensional modeling of diamond growth by microwave plasma activated chemical vapor deposition: Effects of pressure, absorbed power and the beneficial role of nitrogen on diamond growth

A two-dimensional (2D(r, z)) self-consistent model developed and validated in previous studies of diamond deposition processes in microwave (MW) plasma activated chemical vapor deposition reactors is applied in a systematic study of ways in which the gas pressure (over the range p = 75–350 Torr) and absorbed power (P = 1–3 kW) affect the plasma parameters, species distributions and diamond deposition processes from a gas mixture (1%CH4/H2 with 60 ppm added N2) at substrate temperatures (Ts = 1073 and 1323 K) and diameters (ds = 32–100 mm). A more limited set of process conditions for a 0.006%N2/4%CH4/H2 gas mixture and Ts = 1038–1153 K are investigated also. The study traces variations in the global distributions of electron concentration, electron and gas temperature, absorbed power density, key species concentrations and the hydrocarbon interconversion reactions, with particular focus on the radial profiles of CH3 radical and H atom concentrations just above the substrate and on predicted diamond growth rates, G(r). The results and the trends revealed when varying p and P should help guide future optimizations of deposition regimes. The absorbed power density is shown to exhibit quite steep gradients in both the radial (r) and axial (z) directions. This, and the finding of significant power absorption beyond the glowing plasma region, limits the utility of the oft-quoted ‘averaged power density’ as a parameter. The modeling also highlights the essential 2D character of the hydrocarbon interconversion and diffusion transfer processes, which challenges the applicability of any 1D modeling of such MW plasmas. Trace additions of N2 to a MW plasma activated CH4/H2 gas mixture have negligible effect on the plasma parameters or chemistry yet are known to boost the diamond growth rate. A semi-empirical expression for G(r) is developed further to explicitly include the effects of added N2 and a new mechanistic picture presented to account for the observed N-induced enhancements in G. This picture invokes stable moieties such as that formed by CH2 insertion into a CN dimer bond on the 2 × 1 reconstructed (100) diamond surface as ‘anchor’ sites that enable shorter CH2 surface migration lengths and more step-edges for irreversible incorporation of such migrating groups on the growing diamond surface.

Enhanced SO2 adsorption performance on nitrogen-doped biochar: Insights from generalized two-dimensional correlation infrared spectroscopy

Nitrogen-doped biochar is considered as a renewable, cost-effective, and promising SO2 adsorbent. However, it is difficult to improve the physicochemical properties of biochar synergistically and clarify the adsorption mechanism. Therefore, in this study, a one-step high-temperature CO2-NH3 modification method was proposed for biochar to improve its SO2 adsorption, and the in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (in situ DRIFTS) was used to reveal the interface reaction mechanism between SO2 and nitrogen-doped biochar. The results showed that when the modification temperature exceeded 700 °C, CO2 and NH3 exhibited significant thermal activation and nitrogen doping on biochar simultaneously. Under a modification temperature of 800 °C (BCAN-800), the microporous surface area and nitrogen content of modified biochar reached the highest value of 563.83 m2/g and 6.63 wt%. The SO2 adsorption capacities of BCAN-800 were up to 201.89 mg/g and 145.68 mg/g at 30 °C and 120 °C, respectively. The results of in situ DRIFTS showed that dimeric and bridge hydrogen bonds were the main SO2 adsorption sites on nitrogen-doped biochar at 30 °C. With the increase of adsorption temperature, nitrogen-containing groups as the main adsorption site could combine with SO2 to form sulfamide (60 °C), which eventually existed in a more stable form of SO42−/R-O-SO2-OR′ (120 °C).

Crystal packing and mechanofluorochrmism of distyrylanthracene derivatives modulated by hydrogen bonds

Two distyrylanthracene derivatives with ester and carboxyl moieties (AnDMB and AnDBA) were synthesized to investigate the influence of terminal group on their photophysical, crystal stacking and mechanofluorochromic (MFC) properties. Spectral and theory calculation results indicate that two compounds have similar absorption because their similar energy levels although they have different terminal groups. Both compounds exhibited crystallization-induced emission enhancement (CIEE). AnDMB crystals are rod-like and emitted strong blue-green fluorescence because of weak π-stacking. The blocky AnDBA crystals with DMAC (N, N-dimethylacetamide) molecules have a red-shifted emission. Moreover, instead of forming a hydrogen bond dimer between the carboxyl groups, a strong hydrogen bond is formed between the carbonyl group of DMAC and the carboxyl group. Crystal structure indicates that enhanced π-stacking should be responsible for its longer wavelength emission. Moreover, the crystals of two compounds could change their emission colors under force stimuli, but AnDMB exhibited higher color contrast than that of AnDBA. A shift of 40 nm might be observed when the AnDMB crystals were ground, while an emission spectral shift of 18 nm emerged after AnDBA crystals were ground. These results indicated that hydrogen bond did not only regulate molecular stacking and fluorescence properties in crystals, but also adjusted force-stimuli responsiveness.

An atoms-in-molecules characterization of the nature of the OO bond in peroxides and nitroxide dimers.

The quantum theory of atoms-in-molecules (QTAIM) method is used to examine the OO bond in peroxides (RO-OR) and nitroxide dimers (R2 NO-ONR2 ), including Fremy's salt. The electron density (ρ), electron kinetic energy density [K(ρ)], and Laplacian of the electron density (∇2 ρ) at bond critical points characterize the nature of the OO bond. The data distinguish OO bonding of two kinds. Large values of ρ and positive ∇2 ρ and K(ρ) suggest that simple peroxides have charge-shift bonds. Nitroxide dimers, with smaller ρ, positive ∇2 ρ, and near-zero K(ρ), show a lack of shared electron density, suggesting there is no conventional OO bonding in these molecules. QTAIM analysis at the B3LYP/6-311+G(d,p) level of theory gives results in agreement with valence-bond theory and X-ray diffraction characterizations of peroxide OO bonds as charge-shift bonds. In contrast, CCSD/cc-pVDZ calculations fail to agree with previous results because of an insufficient, single-determinant treatment of the charge-shift bond.

How long are Ga⇆Ga double bonds and Ga-Ga single bonds in dicationic gallium dimers?

Syntheses and characterization of two salts [(L)GaGa(L)][pf]2 ([pf]- = [Al(ORF)4]-; RF = C(CF3)3) are reported. They include the first dicationic digallene [(L)Ga⇆Ga(L)]2+ (L = CDPPh = C(PPh3)2) and a digallane [(L)Ga-Ga(L)]2+ (L = [NacNacMes]-). The CDPPh-supported digallene dication includes a trans-bent [L-GaGa-L]2+ bond that is analogous to neutral R-GaGa-R molecules and related to Robinson's famous "Digallyne" [R-GaGa-R]2-. The dicationic digallane [(L)Ga-Ga(L)]2+ is analogous to the widely used "Jones magnesium dimer", but includes a very short GaII-GaII single bond.

COCRYSTAL PREDICTION OF THE SALICYLIC ACIDNICOTINAMIDE

Salicylic acid-nicotinamide was used as a prediction model in the hydrogen bond interactions dominating a cocrystal structure. The combined conformation of the two molecules was analyzed at the B3LYP-D3BJ and WB97M-D3BJ theoretical level. The existing hydrogen bond dimer conformations were compared with putative conformations to determine the bond energy and stability. Some parameters were assessed for predictive descriptors, such as geometric parameters, total energy, interaction energy, single hydrogen bond energy, HOMO-LUMO gap, Laplacian Bond Order, and Natural Bond Orbital. An existing conformation, SACNIC1, produced intermolecular hydrogen bond energy which was quite higher than the other conformations, including the pure homomolecular conformations of either salicylic acid or nicotinamide. The cocrystal packing formation seems to be initiated with SACNIC1 as the basic structure conformation. Furthermore, the presence of the strongest intermolecular hydrogen bond energy in SACNIC1 suggests its potential utility as a predictive descriptor.

Self-Associated 1,8-Naphthalimide as a Selective Fluorescent Chemosensor for Detection of High pH in Aqueous Solutions and Their Hg2+ Contamination.

A novel diamino triazine based 1,8-naphthalimide (NI-DAT) has been designed and synthesized. Its photophysical properties have been investigated in different solvents and its sensory capability evaluated. The fluorescence emission of NI-DAT is significantly impacted by the solvent polarity due to its inherent intramolecular charge transfer character. Moreover, the fluorescence emission quenched at higher pH as a result of photo-induced electron transfer (PET) from triazine moiety to 1,8-naphthalimide after cleaving hydrogen bonds in the self-associated dimers. Furthermore, the new chemosensor exhibited a good selectivity and sensitivity towards Hg2+ among all the used various cations and anions in the aqueous solution of ethanol (5:1, v/v, pH = 7.2, Tampon buffer). NI-DAT emission at 540 nm was quenched remarkably only by Hg2+, even in the presence of other cations or anions as interfering analytes. Job's plot revealed a 2:1 stoichiometric ratio for NI-DAT/Hg2+ complex, respectively.

A new insight on the NO-CO reaction at the electronic level: homogeneous, E-R, and L-H mechanisms.

Carbonaceous surface, as one of the major carriers in coal combustion, was found to exert great influence on the nitric oxide with carbon monoxide (NO-CO) reaction. Although there have been some studies addressing the NO-CO reaction, the inherent mechanism remains obscure. In this work, some updated mechanisms with details were proposed at the electronic level. Using density functional theory calculations, the preferred pathways were identified with three channels consisting of homogeneous, Eley-Rideal (E-R), and Langmuir-Hinshelwood (L-H) heterogeneous reactions. The reasons for the difference in energy barrier among the three mechanisms were revealed by analyzing the chemical bond and electronic transfer. Results show that among these channels, the NO-CO reaction is more likely to occur along the E-R mechanism, due to its lower energy barrier of the rate-determining step. Compared to the L-H mechanism, there is a higher degree of electronic localization between NO molecules at the initial stage of the E-R mechanism. As a result, the NO dimer formation of the E-R mechanism has a lower energy barrier than that of the L-H mechanism. Meanwhile, a large number of electrons floods into the N-N, N-O, and O-O bonds of NO dimer in the homogeneous reaction, which certainly gets more difficult for the dissociation of O atoms in the gas phase. Accordingly, the following stage of N2 formation in the homogeneous reaction has a higher energy barrier than that in both the E-R and L-H reactions. Compared to the L-H mechanism, the E-R mechanism exhibits a lower degree of electronic localization between N2O and carbonaceous surface, suggesting that the interfacial interaction in the E-R mechanism is weaker. As a result, N2 is easier to remove from the carbonaceous surface in the E-R mechanism than in the L-H mechanism. To sum up, the results deepen the knowledge about the NO-CO reaction, which will help to further develop the oxy-fuel combustion technology.

Cyclic Dimers of 4-n-Propyloxybenzoic Acid with Hydrogen Bonds in the Gaseous State.

A comprehensive study of saturated vapors of 4-n-propyloxybenzoic acid (POBA) by gas electron diffraction (GED) and mass spectrometric (MS) methods supplemented by quantum chemical (QC) calculations was carried out for the first time. An attempt was made to detect dimeric forms of the acid in the gaseous state. It has been established that at the temperature of GED experiment, vapor over a solid sample contains up to 20 mol.% of cyclic dimers with two O-H...O hydrogen bonds. The main geometrical parameters of gaseous monomers and dimers of POBA are obtained. The distance r(O…O) = 2.574(12) Å in the cyclic fragment of the gaseous dimer is close to that in the crystal structure (2.611 Å). In the mass spectrum of the POBA recorded the ions of low intensity with a mass exceeding the molecular mass of the monomer were detected. The presence of ions, whose elemental composition corresponds to the dissociative ionization of the dimer, confirms the results of the GED experiment on the presence of POBA dimers in the gas state. The results of GED studies of acetic acid, benzoic acid, and POBA were compared. It is shown that the COOH fragment saves its geometric structure in monomers, as well as the COOH...HOOC fragment with two hydrogen bonds in dimers of different acids. The intermolecular interaction energy in considered acid dimers was estimated using QC calculations (B97D/6-311++G **). The significant value of last (>84 kJ/mol) is the reason for the noticeable presence of dimers in the gas phase.

Competing spin-orbital singlet states in the 4d4 honeycomb ruthenate Ag3LiRu2O6

When spin-orbit-entangled $d$-electrons reside on a honeycomb lattice, rich quantum states are anticipated to emerge, as exemplified by the $d^5$ Kitaev materials. Distinct yet equally intriguing physics may be realized with a $d$-electron count other than $d^5$. We found that the layered ruthenate Ag$_3$LiRu$_2$O$_6$ with $d^4$ Ru$^{4+}$ ions at ambient pressure forms a honeycomb lattice of spin-orbit-entangled singlets, which is a playground for frustrated excitonic magnetism. Under pressure, the singlet state does not develop the expected excitonic magnetism but experiences two successive transitions to other nonmagnetic phases, first to an intermediate phase with moderate distortion of honeycomb lattice, and eventually to a high-pressure phase with very short Ru-Ru dimer bonds. While the strong dimerization in the high-pressure phase originates from a molecular orbital formation as in the sister compound Li$_2$RuO$_3$, the intermediate phase represents a spin-orbit-coupled $J$-dimer state which is stabilized by the admixture of upper-lying $J_{\rm eff} = 1$-derived states. We argue that the $J$-dimer state is induced by a pseudo-Jahn-Teller effect associated with the low-lying spin-orbital excited states and is unique to spin-orbit-entangled $d^4$ systems. The discovery of competing singlet phases demonstrates rich spin-orbital physics of $d^4$ honeycomb compounds and paves the way for realization of unconventional magnetism.

Exploring the mechanism of stilbenes to quench singlet oxygen based on the key structures of resveratrol and its analogues

Stilbenes, especially resveratrol and resveratrol dimers, can quench singlet oxygen (1O2) effectively. Studies found resorcinol, catechol, carbon–carbon double bonds in resveratrol dimers and resveratrol monomers all contributed to quenching 1O2. However, which structures play a key role in quenching of 1O2 by stilbenes had not yet been determined. To explore it, UHPLC-QQQ-MS2 and UHPLC-QTOF-MS2 were used to analyze and compare the 1O2 quenching activities of piceatannol, resveratrol, dihydroresveratrol, pterostilbene, trimethoxystilbene and oxyresveratrol in vitro. The results showed that all six compounds exhibited some capacity to quench 1O2. Catechol [i.e., C6H4(OH)2] had the strongest capacity to quench of 1O2 amongst the stilbenes tested followed by the presence of carbon–carbon double bonds. This offers insight a route for screening for stilbenes with higher activities that might have a role in development of novel food-related antioxidants and functional foods with potential health benefits.

Gold nanoclusters-loaded hydrogel formed by dimeric hydrogen bonds crosslinking: A novel strategy for multidrug-resistant bacteria-infected wound healing.

Restoring skin integrity after wound infection remains a tougher health challenge due to the uncontrolled antibiotic-resistant pathogens caused by antibiotic abuse. Herein, an injectable hydrogel with dual antibacterial and anti-inflammatory activities composed of gold nanoclusters (GNCs) and carbomer (CBM) is developed for wound dressing to overcome multidrug-resistant infection. Firstly, both experimental investigations and molecular dynamics simulation validate the protonation state of 6-mercaptohexanoic acid (MHA) ligands play an important role in its antibacterial action of GNCs. The self-organizing GNCs-CBM composite hydrogel is then spontaneously cross-linked by the dimeric hydrogen bonds (H-bonds) between the MHA ligands and the acrylic acid groups of CBM. Benefitting from the dimeric H-bonds, the hydrogel becomes thickening enough as an ideal wound dressing and the GNCs exist in the hydrogel with a high protonation level that contributes to the enhanced bactericidal function. In all, by combining bactericidal and immunomodulatory actions, the GNCs-CBM hydrogel demonstrated excellent synergy in accelerating wound healing in animal infection models. Hence, the dimeric H-bonds strengthening strategy makes the GNCs-CBM hydrogel hold great potential as a safe and effective dressing for treating infected wounds.

Chemical trends in the high thermoelectric performance of the pyrite-type dichalcogenides ZnS2, CdS2 , and CdSe2

The thermoelectric (TE) properties of the three pyrite-type IIB-${\mathrm{VIA}}_{2}$ dichalcogenides (${\mathrm{ZnS}}_{2}, {\mathrm{CdS}}_{2}$, and ${\mathrm{CdSe}}_{2}$) are systematically investigated and compared with those of the prototype ${\mathrm{ZnSe}}_{2}$ to optimize their TE properties. Using the phonon Boltzmann transport equation, we find that they all have ultralow lattice thermal conductivities. By analyzing their vibrational properties, this is attributed to soft phonon modes derived from the loosely bound rattlinglike metal atoms and to strong anharmonicity caused by the vibrations of all atoms perpendicular to the strongly bound nonmetallic dimers. Additionally, by correlating those properties along the series, we elucidate several chemical trends. We find that the heavier atom masses, larger atomic displacement parameters, and longer bond lengths between metal and nonmetal atoms can be beneficial to the looser rattling behaviors of the metal atoms and therefore lead to the softer phonon modes and that the stronger nonmetallic dimer bonds can boost the anharmonicities, both leading to the lower thermal conductivities. Furthermore, we find that all three compounds have complex energy isosurfaces at valence and conduction band edges that simultaneously allow for large density-of-states effective masses and small conductivity effective masses for both $p$- and $n$-type carriers. Consequently, the calculated TE figures of merit ($ZT$) can reach large values for both $p$- and $n$-type doping. In this paper, we illustrate the effects of the rattlinglike metal atoms and the localized nonmetallic dimers on the thermal transport properties and the importance of different carrier effective masses to electrical transport properties in these pyrite-type dichalcogenides, which can be used to predict and optimize the TE properties of other TE compounds in the future.