Electronic and Functional Scope of Boronic Acid Derived Salicylidenehydrazone (BASHY) Complexes as Fluorescent Dyes

Abstract

A series of boronic acid derived salicylidenehydrazone (BASHY) complexes was prepared and photophysically characterized. The dye platform can be modified by (a) electronic tuning along the cyanine-type axis via modification of the donor-acceptor pair and (b) functional tuning via the boronic acid residue. On the one hand, approach (a) allows the control of photophysical parameters such as Stokes shift, emission color, and two-photon-absorption (2PA) cross section. The resulting dyes show emission light-up behavior in nonpolar media and are characterized by high fluorescence quantum yields (ca. 0.5-0.7) and brightness (ca. 35000-40000 M cm). Moreover, the 2PA cross sections reach values in the order of 200-300 GM. On the other hand, the variation of the dye structure through the boronic acid derived moiety (approach (b)) enables the functionalization of the BASHY platform for a broad spectrum of potential applications, ranging from biorelevant contexts to optoelectronic materials. Importantly, this functionalization is generally electronically orthogonal with respect to the dye's photophysical properties, which are only determined by the electronic structure of the cyanine-type backbone (approach (a)). Rare exceptions to this generalization are the presence of redox-active residues (such a triphenylamine or pyrene). Finally, the advantageous photophysics is complemented by a significant photostability.

Boronic acids as building blocks for the construction of therapeutically useful bioconjugates

“…The conjugation of BAs with Schiff-base ligands enabled the construction of innovative boronic acid salicylidenehydrazone (BASHY) dyes with suitable structural and photophysical properties for live cell bioimaging applications that can be fine-tuned with simple structural modifications. [192][193][194][195][196] These dyes were employed by Gois, Bernardes and co-workers to site-selectively label Annexin V, an early marker of apoptosis, through maleimide technology for the detection of apoptotic cells. The BASHY dye maintained its photochemical and photophysical properties while attached to the biomolecules and the conjugate successfully targeted and detected the apoptotic cells, highlighting BASHY's utility as a promising fluorescent marker for biological imaging (Fig.…”

Cyanine‐Like Boronic Acid‐Derived Salicylidenehydrazone Complexes (Cy‐BASHY) for Bioimaging Applications

“…Multicomponent reactions emerged as a powerful synthetic strategy to generate structurally diverse chromophores [23–26] . In this context we recently reported the assembly of fluorescent boronic‐acid derived salicylidenehydrazone complexes (BASHY) [27, 28] . This multicomponent reaction proved to be synthetically very efficient, which enabled the straightforward construction of a highly flexible platform of functional dyes that were used for the staining of intracellular organelles [27, 29] and the labelling of proteins [30] …”

Azabora[5]helicene Charge‐Transfer Dyes Show Efficient and Spectrally Variable Circularly Polarized Luminescence

“…[18] Much effort has been dedicated to the development of synthetically flexible platforms which enablet he photophysical fine-tuning of the dyes. [3,[9][10][11][19][20][21][22][23][24][25][26][27] As parto fo ur own research program we have developed borylated arylisoquinoline (BAI) dyes,w hich in their N,C-chelate variant are strongly emitting, solvatochromic, and two-photon-absorbing charge-transfer fluorophores with applicationp otentiali nb ioimaging. [9,10,28] With the idea to further enricht he photophysicso ft his fascinating platform we have built on their biaryl structure,w hich providesameanst oa rrive at dyes with helical chirality and the correspondingo bservation of interesting chiropticalp roperties, including the detection of circularly polarized luminescence (CPL).…”