Resonance-Assisted Hydrogen Bonding and π–π Stacking Modulates the Charge Transfer Coupling in Crystalline Naphthothiazoles

Abstract

Supramolecular chemistry employs noncovalent interactions to coax π-conjugated molecules into ordered functional assemblies. Herein, we report 5-methoxynaphtho­[1,2-d]­thiazol-2-amine (NTN) and 4-bromo-5-methoxynaphtho­[1,2-d]­thiazol-2-amine (NTNB) assembled into π-stacked columns integrated by lateral resonance-assisted hydrogen bonds (RAHBs) orthogonal to the π–π stacking direction. Quantum theory of atoms in molecules (QTAIM) and interacting quantum atoms (IQA) analyses were utilized to characterize the presence and stability of intermolecular RAHBs in NTN and NTNB. In contrast to the parallel packing of NTN, bromine substitution promoted antiparallel packing in NTNB with noticeable π–π stacking and orbital overlap favoring efficient charge transfer coupling (V e/h). Antiparallel stacking in NTNB exhibits a dipole moment minimization and aromaticity gain. The relevance of aromaticity in stabilizing π–π stacked systems is highlighted by the aromaticity gain in antiparallel stacked dimers of NTNB and can be extended to estimate the nature and strength of noncovalent interactions. Crystal packing plays a crucial role in regulating the charge transport properties, as can be observed from higher electron and hole transfer coupling along the π–π stacked and RAHB dimer, respectively, in NTN. However, in NTNB maximum electron and hole transfer coupling occurs selectively along the π–π stacked antiparallel dimer. The anisotropic mobility plots from a combination of first-principles quantum chemical calculations and the Marcus–Hush formalism confirm that both RAHB and π–π stacked dimers contribute to the mobility in NTN, but NTNB exclusively benefits from the π–π stacked dimer. Modulating noncovalent interactions for charge carrier transport can harness the innate potential of organic molecules to engineer novel optoelectronic materials.

Photochromism and Photomagnetism in 1,4-bis(4,5-diphenyl-imidazolyl)benzene Chromophores: Water Assisted π-stacks for the Generation of Stable Free Radicals in Solid State

“…In solid state emission spectra, hypsochromic shift of 45 nm was observed for BDPI-II with respect to BDPI-I, that could be the effect of presence of different solvent molecules which influences the stacking of chromophores in the crystal lattice (Figure S11d). [39,40] A similar fluorescence quenching was observed in case of BDPI-II' in comparison with BDPI-II, which suggests the analogous effect of light on both BDPI-I and BDPI-II forms (Figure 1f). In order to explore the reversibility of photochromism under heat, the TGA of both the forms were evaluated.…”

Photoluminescence Behaviors in Self-Assembly Supramolecular Pyridinium Salts

“…In their structure, a molecular stator is served by the 18-crown-6 located on the symmetric plane, while the (methylamino)­pyridinium cations and perchlorate ions lie on two sides regarded as molecular rotors. Meanwhile, a variety of hydrogen bonds exist in these interesting self-assembly supramolecular architectures, further arousing our curiosity, which affects the position and orientation of building blocks and provides an important opportunity to construct crystal structures to further affect physical properties. ,, Detailed hydrogen bonds are listed in Table S2. It is noted that the host 18-crown-6 interacts with guest moieties via dominating N–H···O and weak C–H···O hydrogen bonds as well.…”

“…Meanwhile, a variety of hydrogen bonds exist in these interesting self-assembly supramolecular architectures, further arousing our curiosity, which affects the position and orientation of building blocks and provides an important opportunity to construct crystal structures to further affect physical properties. 30,41,42 Detailed hydrogen bonds are listed in Table S2. S2b), which is different from o-2MAP.…”

Charge Transport through Discrete Crystalline Architectures

“…69 Functionalization of napthothiazoles with bromines aided in forging an ordered zipper structure (Figure 7b) three dimensionally and assisted in transforming the material with selective electron transport, 70 whereas bromine substitution in resonance assisted hydrogen bonded napthothiazole systems imparts an enhancement of charge transfer coupling along the π−π stacking direction due to the tweak in the bromine derivative's crystalline packing. 71 with suitable functionalization can create structurally ordered assemblies with advanced electronic properties.…”

“…Apart from the increased radii of rotation and translation offered by angular naphthothiazole systems to reduce the molecular motions, the appropriate substitutions in the thiazole moiety also impart an effect on the reduction of optical bandgap in the napthothiazole systems . Functionalization of napthothiazoles with bromines aided in forging an ordered zipper structure (Figure b) three dimensionally and assisted in transforming the material with selective electron transport, whereas bromine substitution in resonance assisted hydrogen bonded napthothiazole systems imparts an enhancement of charge transfer coupling along the π–π stacking direction due to the tweak in the bromine derivative’s crystalline packing . While considering charge transport, angular systems outperform linear and quasilinear molecules; therefore, careful design with suitable functionalization can create structurally ordered assemblies with advanced electronic properties.…”