Electron–Phonon Coupling Mediated Self-Trapped-Exciton Emission and Internal Quantum Confinement in Highly Luminescent Zero-Dimensional (Guanidinium)₆Mn₃X₁₂ (X = Cl and Br)

Abstract

We report a large Stokes shift and broad emission band in a Mn-based organic–inorganic hybrid halide, (guanidinium)6Mn3Br12 [GuMBr], consisting of trimeric units of distorted MnBr6 octahedra representing a zero-dimensional compound with a liquid like crystalline lattice. Analysis of the photoluminescence (PL) line width and Raman spectra reveals the effects of electron–phonon coupling, suggestive of the formation of Frenkel-like bound excitons. These bound excitons, regarded as the self-trapped excitons (STEs), account for the large Stokes shift and broad emission band. The excited-state dynamics was studied using femtosecond transient absorption spectroscopy, which confirms the STE emission. Further, this compound is highly emissive with a PL quantum yield of ∼50%. With chloride ion incorporation, we observe enhancement of the emissive properties and attribute it to the effects of intrinsic quantum confinement. Localized electronic states in flat bands lining the gap and their strong coupling with phonons are confirmed with first-principles calculations.

Elucidating Structure–Property Correlation in Perovskitoid and Antiperovskite Piperidinium Manganese Chloride

“…In addition, the PLQY of compound 1 is ∼28.3%. On the other hand, the antiperovskite compound 2 exhibits a PLQY of 54.5% (Figure S10) due to the confinement effect resulting from the reduction of lattice dimensionality. , The higher Mn–Mn separation in compound 2 compared to that in compound 1 might be another plausible reason leading to higher PLQY in the former compound and concurred with the design principle of Mn-based OIH reported by Mao et al The PLQYs of compounds 1 and 2 in comparison to other 1D and 0D compounds are mentioned in Tables S4 and S5, respectively.…”

Halogen Bond Induced Structural and Photophysical Properties Modification in Organic–Inorganic Hybrid Manganese Halides

“…Over the past few years, the organic–inorganic hybrid (OIH) metal halides sprung up as a forefront candidate for light harvesting. − The OIHs inherit the merits of both organic and inorganic semiconductors in a single system exhibiting exciting photovoltaic and optoelectronic properties. − The unique structure–property relationship includes a soft liquid-like crystalline lattice, white light emission, high photoluminescence quantum yield, ferroelectricity, piezoelectricity, and magnetism. − But, the low stability of OIHs is the key challenge for their real-world application. As a result, different supramolecular interactions (noncovalent) have been employed as a tool for crystal engineering, and among them, halogen bonding (XB) is a new paradigm. , XB is an attractive noncovalent interaction among an electrophilic halogen atom (Lewis acid) with a nucleophilic group (neutral or anionic, Lewis base) of the same or different entities. , The covalently bonded electronegative halogen atom creates a σ-hole and a positive electrostatic potential on its surface and acts as an XB donor (electron acceptor) to an electron-rich site (XB acceptor). , The existence of the σ-hole governs the directionality, while the polarizability of the halogen atom tunes the strength of XB, leading to fascinating properties. , Early research on XB was limited to supramolecular chemistry. − But, recently, the role of XB was explored to enhance curie temperature and piezoelectric response in ferroelectric hybrid lead halides .…”

Red‐Emitting Organic–Inorganic Hybrid Manganese(II) Halides for X‐Ray Imaging

“…[34,35] The unusual 0D structure of (Gua) 2 MnCl 4 may be attributed to the presence of supramolecular ion pair interactions between the Gua + cations, which inhibits the extension of the 1D chain, thus resulting in the 0D structure of trimeric unit. [36,37] The bond lengths and bond angles of [MnCl 6 ] 4− octahedron are listed in Table S2 (Supporting Information). It can be seen that the [MnCl 6 ] 4− octahedron has a slight distortion.…”