Crystalline transformations of dinaphthyridinylamine derivatives with alteration of solid-state emission in response to external stimuli

Abstract

Dinaphthyridinylamine derivatives, IJ1,8Nap) 2 NR (R = H (1), Me (2) and Ph (3)), were prepared as fluorophores in response to external stimuli. From crystallization, single crystals (1) containing water molecules as crystal solvents and crystal polymorphs (3-α and 3-β) containing MeOH molecules were obtained. In the crystal packing of 1, a γ-herringbone (γ-HB) fashion with π-π interaction was observed. In contrast, the packing of 3-α was in a HB fashion with intermolecular CH-N interaction, while the packing of 3-β was in a slipped columnar fashion with π-π interaction between the naphthyridine planes. The observed difference of crystal packings influenced the solid-state emission spectra. Crystals 1, 2 and 3 showed piezochromic behaviors, in which by thoroughly grinding the crystals, the solid-state emission blue color (λ f max = ca. 450 nm) turned into yellowish green (λ f max = ca. 510 nm) for the amorphous solid. In addition, crystals 3-α and 3-β showed various phase transitions including single-crystal-to-single-crystal (SCto-SC) transformation in response to external stimuli. Crystal 3-β desorbed the MeOH molecules under ambient atmosphere to provide crystal 3-β′ (λ f max = 449 nm), while the resulting crystal 3-β′ returned to crystal 3-β upon exposure to MeOH vapor, indicating vapochromic behavior. Furthermore, crystal 3-β′ was heated at ca. 160°C to afford crystal 3-α (SC-to-SC transformation). The gummy oil in the resulting supercooled liquid (SCL) state after melting the crystals was scratched by using a fine wire at and above 80°C (>T g , glass temperature) to form crystal 3-α with blue emission (SCL-to-SC transformation). CrystEngCommThis journal is

Fluorescence Properties and Exciplex Formation of Emissive Naphthyridine Derivatives: Application as Sensors for Amines

“…Reduction of 2 with tin afforded 2‐chloro‐3,5‐diaminopyridine ( 3 ) as a white solid. Finally, by Combes synthesis in the presence of hexafluoroacetylacetone and montmorillonite K10 as catalyst, 15Nap‐Cl was obtained as a yellowish solid.…”

“…H 2 SO 4 , fuming HNO 3 , NaOH, POCl 3 Na 2 CO 3 , MgSO 4 , 35 % HCl solution, Sn powder, and hexafluoroacetylacetone were purchased from Nacalai Tesque Co. Ltd., Fujifilm Wako Pure Chemical Co. Ltd., Sigma‐Aldrich, or Tokyo Chemical Industry Co., Ltd. Compounds 1 and 2 were prepared according to the previously reported procedures . Silica gel for column chromatography was purchased from Kanto Chemical Ltd., Japan.…”

“…We have studied push–pull‐type fluorophores consisting of aminoquinoline ( TFMAQ ) or aminonaphthyridine ( 18Nap ) derivatives, which show fluorescence changes in response to various external stimuli such as solvent, heat, protons, light, scratching, grinding, and vapor . Recently, tricyclic amidine derivatives DHIm and DHPy , in which a dihydroimidazole or dihydropyrimidine ring is fused with the 18Nap framework, have been reported to exhibit fluorescence changes in response to a proton source (Scheme ) …”

“…[9,10] We have studied push-pull-type fluorophores consisting of aminoquinoline (TFMAQ) [11] or aminonaphthyridine (18Nap) derivatives, [12] which show fluorescencec hanges in response to variouse xternal stimuli such as solvent, [11] heat, [11][12][13] protons, [14] light, [15] scratching, [16] grinding, [17] and vapor. [18] Recently, tricyclic amidined erivatives DHIm and DHPy,i nw hich ad ihydroimidazoleo rd ihydropyrimidine ring is fused with the 18Nap framework, have been reported to exhibitf luorescence changes in response to ap roton source (Scheme 1). [14] In this study,t od evelop an amine sensor based on pushpull-type fluorophores, we prepared an aphthyridine derivative that shows af luorescencer esponse to amines, namely 2chloro-6,8-bis(trifluoromethyl)-1,5-naphthyridin-3-amine (15Nap-Cl).…”

Photophysical Properties of Emissive Pyrido[3,2‐c]carbazole Derivatives and Apoptosis Induction: Development towards Theranostic Agents in Response to Light Stimulus

“…Here, we have developed three promisinge missive compounds,f rom emissive aminoqunoline derivatives, TFMAQ, and aminonaphthyridine derivatives, 1,8-Nap (Figure1) [15][16][17][18][19][20][21][22][23] that respondt ov arious external stimuli. Recently,w er eported that tricyclic amidine derivatives fused with ap yrimidine (DHPy)r ing or incorporation of an imidazole (DHIm)r ing into a1 ,8-naphthyridine frameworks showed changes in fluorescence that are triggered by acidic protons and metal ions ( Figure 1).…”