Alkali metals doped cycloparaphenylene nanohoops: Promising nonlinear optical materials with enhanced performance

Acceptor engineering of quinone-based cycloparaphenylenes via post-synthesis for achieving white-light emission in single-molecule

Developing donor-acceptor [n]cycloparaphenylenes (D-A [n]CPPs) with multiple emissions from different emissive states remains challenging yet crucial for achieving white-light emission in single-molecule. Here, we report our explorations into acceptor engineering of quinone-based D-A [10]CPPs (Nq/Aq/Tq[10]CPPs) via a post-lateral annulation using Diels-Alder reactions of oxTh[10]CPP. X-ray analysis reveals that Nq[10]CPP displays a side by side packing via naphthoquione stacking while Aq[10]CPP adopts an intercalated conformation through anthraquinone interaction. Fluorescence investigations reveal that the quinone-based [10]CPPs display distinctive acceptor-dependent dual-emission from both the locally excited state and charge transfer state after single-wavelength excitation in organic solvents, consequently leading to multicolor emissions, in particular, white-light emission in CHCl3 for Aq[10]CPP. In THF/water mixture, quinone-based [10]CPPs and oxTh[10]CPP display a wide range of fluorescence emissions including white-light emission as increasing the fraction of water, accompanying by the formation of nanoparticles as demonstrated by Tyndall effect and SEM. Interestingly, the fluorescence of Aq[10]CPP can be switched from white to blue in CHCl3 upon redox. Our investigations demonstrate that acceptor engineering not only endows quinone-based [10]CPPs with two distint emissive states for achieving white-light emission but also highlights an effective post-synthetic strategy for functionalizing CPP nanohoops with desirable properties.

Realizing the effect of s-block metals on a charge transfer crystal of indol-2-one for enhanced NLO responses with efficient energetic offsets

CONTEXT

Due to their unique photophysical properties, organic charge transfer crystals are becoming promising materials for next-generation optoelectronic devices. This research paper explores the impact of s-block metals on a charge transfer crystal of indol-2-one for enhanced nonlinear optical (NLO) responses with efficient energetic offsets. The study reveals that alkali metals can enhance NLO performance due to their free electrons.

METHOD

The Perdew-Burke-Ernzerhof functional of DFT with dispersion correction (D3) was used, and the λmax values ranged between 596 and 669 nm, with the highest value for dichloromethane (DCM). Leveraging the unique properties of metals allowed for the development of nonlinear optical materials with improved performance and versatility. Softness (σ) values provide insight into electron density changes, with higher values indicating a greater tendency for changes and lower values indicating the opposite. The NLO results for the chromophores MMI1-MMI6 show varying linear polarizability (< α0 >) along with their first (β0) and second (γ0) hyperpolarizabilities. Chromophore MMI4 stands out with the highest NLO performance, having two potassium (K) atoms. Its < α0 > , β0, and γ0 values of 4.19, 7.09, and 17.43 (× 10-24 e.s.u), respectively, indicate a significant enhancement in NLO response compared to the other chromophores. The transitions involving (O20)LP → (C3-N5)π* and (O19)LP → (N12-C13)π* exhibit the highest level of stabilization, followed by (O23)π → (C10-C11)π*, while (C6-N12)π → (C6-C7)π* shows the lowest level of stabilization for chromophore MMI4. The present research work is facile in its nature, and it can be helpful for synthetic scientist to design the new materials for uniting crystal properties with metal doping for efficient NLO devices.