Negative electron binding energies observed in a triply charged anion: Photoelectron spectroscopy of 1-hydroxy-3,6,8-pyrene-trisulfonate

Abstract

We report the observation of negative electron binding energies (BEs) in a triply charged anion, 1-hydroxy-3,6,8-pyrene-trisulfonate (HPTS(3-)). Low-temperature photoelectron spectra were obtained for HPTS(3-) at several photon energies, revealing three detachment features below 0 electron BE. The HPTS(3-) trianion was measured to possess a negative BE of -0.66 eV. Despite the relatively high excess energy stored in HPTS(3-), it was observed to be a long-lived anion due to its high repulsive Coulomb barrier (RCB) ( approximately 3.3 eV), which prevents spontaneous electron emission. Theoretical calculations were carried out, which confirmed the negative electron BEs observed. The calculations further showed that the highest occupied molecular orbital in HPTS(3-) is an antibonding pi orbital on the pyrene rings, followed by lone pair electrons in the peripheral -SO(3) (-) groups. Negative electron BE is a unique feature of multiply charged anions due to the presence of the RCB. Such metastable species may be good models to study electron-electron and vibronic interactions in complex molecules.

Highly photostable “super”-photoacids for ultrasensitive fluorescence spectroscopy

“…The use of HPTS in such assays is hampered by its low photostability which is assumed to arise from the permanent negative charges. 78,79 Especially for microscopic applications, a good photostability is a key feature. Since all dyes are sufficiently soluble in water for FCS measurements, we determined their relative photostability in aqueous buffer solution ( pH = 7.5) by the use of this technique.…”

Excited states of multiply-charged anions probed by photoelectron imaging: riding the repulsive Coulomb barrier

“…This was first shown for a tetra-sulphonated cyclic copper phthalocyanine tetra-anion and has subsequently been observed in a number of other MCAs. 25,[28][29][30][31] As the energy of A nÀ lies above the A (nÀ1)À + e À asymptote, the electron can tunnel through the RCB. If the energy difference between A nÀ and A (nÀ1)À is small relative to the RCB, then the lifetimes for electron loss by tunnelling can be sufficiently long (4ms) for the MCA to be isolated by mass-spectrometry.…”

Development of a low-temperature photoelectron spectroscopy instrument using an electrospray ion source and a cryogenically controlled ion trap

“…The initial construction of the low-temperature instrument was finished in late 2004. Since then cold PES spectra of a variety of anions have been obtained and reported [46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64] while we were debugging and making further improvements to this fairly complex instrument. The effects of temperature on the quality of the obtained PES data are dramatic.…”