Sensor activity and logic behaviour of PET based dihydroimidazonaphthalimide diester

A Tutorial Review on the Fluorescent Probes as a Molecular Logic Circuit-Digital Comparator

The rapid progress in the field of fluorescent probes and fluorescent sensing material extended this research area toward more complex molecular logic gates capable of carrying out a variety of sensing functions simultaneously. These molecules are able to calculate a composite result in which the analysis is not performed by a man but by the molecular device itself. Since the first report by de Silva of AND molecular logic gate, all possible logic gates have been achieved at the molecular level, and currently, utilization of more complicated molecular logic circuits is a major task in this field. Comparison between two digits is the simplest logic operation, which could be realized with the simplest logic circuit. That is why the right understanding of the applied principles during the implementation of molecular digital comparators could play a critical role in obtaining logic circuits that are more complicated. Herein, all possible ways for the construction of comparators on the molecular level were discussed, and recent achievements connected with these devices were presented.

Design and Synthesis of a Novel ICT Bichromophoric pH Sensing System Based on 1,8-Naphthalimide Fluorophores as a Two-Input Logic Gate and Its Antibacterial Evaluation

The synthesis, sensor activity, and logic behavior of a novel 4-iminoamido-1,8-naphthalimide bichromophoric system based on a "fluorophore-receptor" architecture with ICT chemosensing properties is reported. The synthesized compound showed good colorimetric and fluorescence signaling properties as a function of pH and proved itself as a promising probe for the rapid detection of pH in an aqueous solution and base vapors in a solid state. The novel dyad is able to work as a two-input logic gate with chemical inputs H⁺ (Input 1) and HO^- (Input 2) executing INHIBIT logic gate. The synthesized bichromophoric system and the corresponding intermediates demonstrated good antibacterial activity toward Gram (+) and Gram (-) bacteria when compared with the Gentamycin standard.

Low Molecular Weight Probe for Selective Sensing of PH and Cu2+ Working as Three INHIBIT Based Digital Comparator

A novel simple molecular chemosensor 2 was synthesized and examined for pH, cations and anions detection. At pH values higher than 10, probe 2 switches on a green emission where the excited state intramolecular proton transfer (ESIPT) is ceased. Also, the probe absorption spectrum shows a clear pH dependence, and the probe aqueous solution (ethanol/water = 1:2, borate buffer) responds selectively and sensitively through its fluorescence spectrum to the presence of Cu²⁺. Job's plot gave a 2:1 stoichiometry of Probe-2/Cu²⁺ complex, which responds to the presence of S^2- and H₂PO₄^- in aqueous solution (ethanol/water = 1:2, borate buffer) by its absorption and fluorescence spectra. In addition, probe 2 mimics a digital comparator based on three INHIBIT logic gates by different outputs using HO^- and H⁺ as inputs. Moreover, probe 2 also executes AND and NOT TRANSFER logic gates using Cu²⁺ and S^2- as inputs.

A chemosensoring molecular lab for various analytes and its ability to execute a molecular logical digital comparator

We reported here the unique ability of a Rhodamine 6G-based probe (3) to detect discriminately several targets, including H⁺, HO^-, Cu²⁺, Hg²⁺, Fe³⁺, Co²⁺, Cd²⁺, Zn²⁺, Sn²⁺, Ni²⁺, Al³⁺, Pb²⁺, Ce³⁺and Ag⁺, by unambiguously colorimetric and fluorimetric outcomes. In aqueous solutions, the presence of proton induced the ring-opening of rhodamine moiety but the presence of hydroxide induced the conversion of 2-hydroxyphenyl hydrazone moiety from the non-fluorescent benzenoid form into the fluorescent quinoid form. The probe could to distinguish between different cations in DMF and to work like an artificial tongue at molecular level. Several logic gates including OR, INHIBIT and TRANSFER, were performed by the probe. Moreover, the probe is able to execute three INHIBIT logic gates by two inputs, which was exploited to execute a digital molecular comparator.

Synthesis of a single 1,8-naphthalimide fluorophore as a molecular logic lab for simultaneously detecting of Fe3+, Hg2+ and Cu2

A novel fluorescence sensing 1,8-naphthalimide fluorophore is synthesized and investigated. The novel probe comprising two different binding moieties is capable to detect selectively Fe³⁺ over the other representative metal ions as well as a combination of biologically important cations such as Fe³⁺, Cu²⁺ and Hg²⁺ in the physiological range without an interfering effect of the pHs. Due to the remarkable fluorescence changes in the presence of Fe³⁺, Hg²⁺ and Cu²⁺ ions, INH and AND logic gates are executed and the system is able to act as a single output combinatorial logic circuit with three chemical inputs.

A dithienosilole-based fluorescent chemosensor for multiple logic operations at the molecular level

A chemosensor consisting of two terpyridines covalently linked to a dithienosilole unit (1) has been synthesized, and its optical and metal sensing properties have been investigated. Due to the metal-organic coordination function, 1 can bind with many transition metal ions and display different fluorescence responses that cause it to function as a "turn-off" fluorescent chemosensor. A significant bathochromic shift in the fluorescence spectra is observed in the presence of Zn(2+). Meanwhile, the emission of 1 is weakened upon exposure to Ag(+) and Fe(2+) and completely quenched by Ni(2+), Co(2+), and Cu(2+). Based on the observed results, several logic gates, such as XNOR, INHIBIT, and IMPLICATION, have been achieved by controlling the chemical inputs.

Novel nanosized water soluble fluorescent micelles with embedded perylene diimide fluorophores for potential biomedical applications: cell permeability, localization and cytotoxicity

Novel biocompatible water-soluble fluorescent micelles with embedded perylene diimides (PDI) for intracellular applications have been prepared by self assembling of amphiphilic poly(vinyl alcohol)-b-poly(acrylonitrile) (PVA-b-PAN) copolymers in the presence of synthesized fluorophores. Amphiphilic PVA-b-PAN copolymers were obtained by selective hydrolysis of well-defined poly(vinyl acetate)-b-poly(acrylonitrile) (PVAc-b-PAN) copolymer. The preparation of the novel fluorescence micelles consisting of PVA hydrophilic shell and PAN hydrophobic core with incorporated PDI fluorophores has been confirmed by DLS and TEM analysis. The cytotoxicity of the water-soluble fluorophores and their internalization into living cells depending on the micellar concentration have been tested. It was shown that they could successfully enter in living cells without destroying their morphology. The results obtained indicate that the novel water-soluble fluorescent micelles with embedded PDI fluorophores would be suitable for potential intracellular biomedical applications.

A highly selective ratiometric fluorescent pH probe based on a PAMAM wavelength-shifting bichromophoric system

A novel PAMAM wavelength-shifting bichromophoric system has been successfully developed. Novel compound was configured as a light harvesting antenna where the system surface is labeled with yellow-green emitting 4-(N,N-dimethylamino)ethylamino-1,8-naphthalimide "donor" units capable of absorbing light and efficiently transferring the energy to a focal Rhodamine 6G "acceptor". The periphery of the system was designed on the "fluorophore-spacer-receptor" format, capable of acting as a molecular fluorescence photoinduced electron transfer based probe. Due to the both effects, photoinduced electron transfer in the periphery of the system and pH dependent rhodamine core absorption, novel antenna is able to act as a selective ratiometric pH fluorescence probe in aqueous medium. Thus, the distinguishing features of the fluorescence resonance energy transfer systems were successfully combined with the properties of classical ring-opening charge transfer systems, which may be beneficially for monitoring pH variations in complex samples.

Synthesis and sensor activity of a PET-based 1,8-naphthalimide Probe for Zn(2+) and pH determination

A novel blue-emitting 1,8-naphthalimide fluorophore designed as a molecular PET-based probe for determination of pH and detection of transition metal ions in the environment was successfully synthesized. Novel compound was configured on the "fluorophore-spacer-receptor" format. Due to the tertiary amine receptor the novel system showed "off-on" switching properties under the transition from alkaline to acid media (FE = 3.2) and in the presence of Zn(2+) ions (FE = 2.5). The results obtained illustrate the high potential of the synthesized blue-emitting 1,8-naphthalimide fluorophore as an efficient pH chemosensing material and a selective probe for Zn(2+) ions.