New Fluorescent Model Compounds for the Study of Photoinduced Electron Transfer: The Influence of a Molecular Electric Field in the Excited State

Abstract

lenides 2 in 50-XOViO yields a s yellow oils. Selected spectroscopic data for 2f: 'HNMR(300MHz.CDCIJ:ii = 0.82(t.J=7.0Hz.bHj.1 65(dq.J=7.0,7.0 Hz, 4Hj. 2.2X Is, 2H). 4.76 (t. J =7.0 Hz. 2 H). 7.19 (dd. J = 7 5, 7.5 Hz, 2H). 7.33 (dd..~=~. S ,~. S H Z ,~H ) .~.~S (~. J =~.~H~.~H ) .~.~S (~. J =~S H~.~H ) :~~C N M R (75 MH7. CDCI,): 6 =10.3, 31.3. 74.7. 126.4, 128.3. 129.1. 130.0. 135.3. 146.5: "Se N M R (76 MHz, CDCI,): d = 456.1: [1]:" = + 262.0 ( c = I , CHCI,,): correct elemental analysis foi-C,,H,,0,Se2.Addition ofthe diselenides 2 to atyrene: 2 (0.1 nimol) was placed in dry diethyl ether (4 inL) under argon 'it -78°C and bromine (0.1 1 minol. 0.1 1 mL of a 1 M solutioii in CCI,) wis added. After 10 min silver triflate (72 mg. 0.28 minol) in methanol (0.1 mL) was added atid the mixture was stirred for 20 min at -78 ~ C. The reaction solution s a s cooled to -100 C and treated with styrene (0.4 mmol, 0.046 mL). After the mixture had been stirred Tor 2 h. .~~r~i.-colIidine (0.3 mniol, 0.04 inL) was added. ;ind the resultant mixture was heated to 20 C and washed with 7 % aqueous citric acid solution ( 5 mL). The organic phase was dried with MgSO,. and after remowl of the solwnt under vacuum. thc addition product 3 was purilied by column chroinatosraphy on silica (pentnne: rrrr-butylmethyl ether 3 : I ) . Selected apectroscopic data for 3f. 'H NMR (300 MHz. CDCI,): 6 = 0.98 (t. J =7.4 HL. 3H). 1.79 (quin,J =7.4H7. 2H). 2.41 (s. IH). 3.10-3 30(m. 2H). 3.24(s. 3Hj.4.36 (dd. J = 8 5. 5 HL. I H ) , 5.04 (in. 1Hj. 7.13-7.51 (m. 9H); "C NMR (75 MHz. 139.7. 133.7, 140 8. 140 0: correct elemental analysis Ibr C',,H,,O,Se.

Early warning smartphone diagnostics for water security and analysis using real-time pH mapping

“…3. When the data are fitted to the Henderson-Hasselbalch equation, the calculated acid dissociation constant (pKa=8.6) is very close to the reported values for this type of probe [43]; the small variation observed is presumably due to the different solvent system used. The calibration equation was then uploaded to the app to enable pH measurements of field samples.…”

“…The pH probe used in this work is the thermally stable, easily prepared, and photo-induced electron transfer (PET) dye 4-aminonapthalimide [43]. The absorption maximum of this probe (λ abs ~ 444 nm) with a 3 dB bandwidth of ~ 70 nm aligns well with the wavelength of filtered light from the camera flash (emission peak at ~ 437 nm) [7].…”

The pH-dependent fluorescence of pyridylmethyl-4-amino-1,8-naphthalimides

“…One system based on 1,3-diaryl-∆ 2 -pyrazoline ICT fluorophores has been reported by us 8 before, but in this instance the pyridyl group was positioned almost along the bisector of the transition dipole of the ICT state so that no electric field effects were expected or seen. The previous examination of ICT fluorophores such as 4-amino-1,8-naphthalimides with aminoalkyl side-chains revealed strong regiochemical dependence of the pH-switching efficiency, 13,14 which suggested unidirectional PET processes. [13][14][15][16] PET from the amine to the fluorophore occurred only when the former was connected to the 4-amino group of the fluorophore.…”

“…The previous examination of ICT fluorophores such as 4-amino-1,8-naphthalimides with aminoalkyl side-chains revealed strong regiochemical dependence of the pH-switching efficiency, 13,14 which suggested unidirectional PET processes. [13][14][15][16] PET from the amine to the fluorophore occurred only when the former was connected to the 4-amino group of the fluorophore. Unidirectional PET is most famously observed in the bacterial photosynthetic reaction centre, 17 and analogous behaviour in small molecules should permit easier analysis of the phenomenon.…”

Building pH Sensors into Paper-Based Small-Molecular Logic Systems for Very Simple Detection of Edges of Objects

“…47 Edge detection was not an issue in these studies. Following our discovery of the fluorescent PET sensing capabilities of the 4-(aminoalkyl)-aminonaphthalimide system, 48 it was developed into metal sensing applications by Roche Diagnostics in consultation with us 49,50 and it was also taken up by many others. 39,[51][52][53][54][55] So it is natural that many of us would continue to exploit the useful properties of this molecular motif: hence, our use of sensors 1 and 4 in the current work.…”