Theoretical Design of n-Type Organic Semiconducting Materials Containing Thiazole and Oxazole Frameworks

Entropy-ruled nonequilibrium charge transport in thiazolothiazole-based molecular crystals: a quantum chemical study

The charge and energy fluctuations in molecular solids are crucial factors for a better understanding of charge transport (CT) in organic semiconductors. The energetic disorder-coupled molecular charge transport is still not well-established. Moreover, the conventional Einstein's diffusion (D)-mobility (μ) relation fails to explain the quantum features of organic semiconductors, including nonequilibrium and degenerate transport systems, where kB is the Boltzmann constant, T is the temperature and q is the electric charge. To overcome this issue, a unified version of the entropy-ruled D/μ relation was proposed by Navamani (J. Phys. Chem. Lett., 2024, 15, 2519-2528) for hopping and band transport systems as where d, η and heff are the dimension (d = 1, 2, 3), chemical potential and effective entropy, respectively. Within this context, we investigate the CT properties of 2,5-bis(4-methoxyphenyl)thiazolo[5,4-d]thiazole (MOP-TZTZ) and 2,5-bis(2,4,5 trifluorophenyl)-thiazolo[5,4-d]thiazole (TFP-TZTZ) molecular solids using electronic structure calculations and the entropy-ruled method. The CT key parameters such as charge transfer integral and site energy are computed by matrix elements of the Kohn-Sham Hamiltonian. Using Marcus theory, the charge transfer rate is numerically calculated for MOP-TZTZ and TFP-TZTZ molecular crystals under different site energy disorder (ΔEij(E⃑)) situations. Using our entropy-ruled method, the exact diffusion-mobility (D/μ) and other transport quantities such as thermodynamic density of states, conductivity, and current density are calculated for these derivatives at different applied electric field values via the site energy disorder. The theoretical results show that the molecule TFP-TZTZ has good hole mobility (∼0.012 cm2 V-1 s-1) at a site energy disorder value of 90 meV. The obtained ideality factor from the Navamani-Shockley diode current density equation categorizes the typical transport as either the Langevin-type or Shockley-Read-Hall mechanism in the studied molecular solids. Our analysis clearly shows that both the electron and hole transport in these MOP-TZTZ and TFP-TZTZ molecules follow the trap-free Langevin mechanism, which is indeed ideal for designing charge-transporting molecular devices.

Arylation of benzazoles at the 4 positions by activation of their 2-methylsulfinyl groups

Treatment of 2-methylsulfinylbenzazoles with triflic anhydride in the presence of phenols yields the corresponding 4-(p-hydroxyphenyl)-2-methylsulfanylbenzazoles. This regioselective dehydrative C-H/C-H coupling arylation represents a rare example of functionalizations on the benzene rings of benzo-fused azoles.

Photochemical Synthesis and Electrochemical and Photophysical Properties of 2,7-Diarylbenzo[1,2-d:4,3-d']bis(thiazoles)

This article focuses on the development of practical approaches to the preparation of benzo[1,2-d:4,3-d']bis(thiazoles) using blue light-induced photochemical cyclization of N,N'-(1,4-aryl)dithioamides in the presence of p-chloranil as a mild oxidant. The proposed method allows to obtain benzo[1,2-d:4,3-d']bis(thiazoles) containing donor substituents in the conjugated chain. Photophysical and (spectro)electrochemical properties of 2,6-di([2,2'-bithiophen]-5-yl)benzo[1,2-d:4,3-d']bis(thiazole) and -benzo[1,2-d:4,5-d']bis(thiazole) are studied in detail. The properties of the synthesized compounds suggest their potential applications for organic electronics.

Gold-catalyzed synthesis of oxazoles from alkynyl triazenes and dioxazoles

A gold-catalyzed regioselective [3 + 2] cycloaddition of alkynyl triazenes with 1,2,4-dioxazoles was developed.

Consecutive O-S/N-S Bond Cleavage in Gold-Catalyzed Rearrangement Reactions of Alkynyl N-Sulfinylimines

Gold-catalyzed reactions of alkynyl N-sulfinylimines were used to produce the corresponding 2H-azirines possessing sulfenyl and acyl groups at the 3-position of the azirine ring in good to excellent yields. These reactions involved internal transfer of the sulfinyl oxygen atom to form a thiooxime intermediate tethered to an α-oxo gold carbene moiety. Subsequent insertion of the carbene into the N-S bond resulted in ring construction.

Access to highly substituted oxazoles by the reaction of α-azidochalcone with potassium thiocyanate

The reactivity of α-azidochalcones has been explored for the preparation of highly substituted oxazoles via a 2H-azirine intermediate. The azidochalcones, when treated with potassium thiocyanate in the presence of potassium persulfate, lead to 2,4,5-trisubstituted oxazoles in good yields. Incidentally, 2-aminothiazoles are the products when ferric nitrate is employed instead of persulfate in the above reaction.

Effects of the terminal donor unit in dyes with D-D-π-A architecture on the regeneration mechanism in DSSCs: a computational study

This theoretical study on dye-sensitized solar cells (DSSCs) includes design strategies for dye donor units to improve the efficiency of DSSCs, and further illuminates the organic dye regeneration mechanism. We have designed a series of new organic sensitizers based on a D-D-π-A architecture to exhibit easy electron transfer and to have remarkable light harvesting properties in the visible region by density functional theory (DFT) and time-dependent (TD)-DFT calculations. Furthermore, the interaction of the organic sensitizers with the conventional redox electrolyte using the triiodide/iodide couple (I3-/I-) is investigated. Our calculations indicate that incorporation of strong electron-donating groups remarkably improves the charge transfer characteristics, optoelectronic properties and rapid dye regeneration as compared to less electron donating substituents. In addition, our study demonstrates the possibility of second electron injection from the oxidized dye complex to the semiconductor surface, which further confirms our recently proposed dye regeneration mechanism.

Alkynyl Thioethers in Gold-Catalyzed Annulations To Form Oxazoles

Non-oxidative, regioselective, and convergent access to densely functionalized oxazoles is realized in a functional-group tolerant manner using alkynyl thioethers. Sulfur-terminated alkynes provide access to reactivity previously requiring strong donor-substituted alkynes such as ynamides. Sulfur does not act in an analogous donor fashion in this gold-catalyzed reaction, thus leading to complementary regioselective outcomes and addressing the limitations of using ynamides.

Charge Transport in Molecular Materials: An Assessment of Computational Methods

The booming field of molecular electronics has fostered a surge of computational research on electronic properties of organic molecular solids. In particular, with respect to a microscopic understanding of transport and loss mechanisms, theoretical studies assume an ever-increasing role. Owing to the tremendous diversity of organic molecular materials, a great number of computational methods have been put forward to suit every possible charge transport regime, material, and need for accuracy. With this review article we aim at providing a compendium of the available methods, their theoretical foundations, and their ranges of validity. We illustrate these through applications found in the literature. The focus is on methods available for organic molecular crystals, but mention is made wherever techniques are suitable for use in other related materials such as disordered or polymeric systems.

Crystal structure and modeled charge carrier mobility of benzobis(thiadiazole) derivatives

Benzobis(thiadiazole) derivatives showed a large diffusion coefficient between the molecules located in the co-planar and the standard π–π stacking directions.

Mechanism of the gold(i)-catalyzed synthesis of imidazo-pyrimidines and imidazo-pyrazines via [3 + 2] dipolar cycloaddition: a DFT study

The mechanisms of gold(i)-catalyzed [3 + 2] cycloaddition reactions of pyridinium N-(heteroaryl)-aminides with alkynes have been investigated using DFT calculations.

A theoretical study on charge transport of dithiolene nickel complexes

The effect of chemical structures on the charge transport characteristics of dithiophene nickel complexes was studied using DFT and NEGF-DFT methods.

Synthesis of substituted oxazoles from enamides

2,5- and 2,4,5-substituted oxazoles were prepared in one-pot by the NBS/Me₂S-mediated cyclization of enamides in the presence of base.