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This review highlights recent advances in new high sensitive and selective fluorescent chemosensors for metal ions based on the dipyrromethene platform with the advantages of bright color, significant fluorescence changes and simple structural functionalization. The most interesting results from studies on cationic sensors' structure and properties in organic, aqueous-organic, physiological media, and in cells are presented. The review includes a description of the main characteristics of fluorescent sensors which have been recently synthesized for a number of alkali, alkaline earth and mainly transition metal cations on the basis of open-chain oligopyrrole ligands such as dipyrromethenes, tripyrrins (prodigiosin-type), bis(dipyrromethene)s and boron(III) dipyrromethene (BODIPY). It was shown that the hybrid molecules, built from BODIPY and other similar chelating ligands, are effective fluorescent chemosensors on various metal cations, depending on the receptor fragment nature, but are very difficult to obtain. Dipyrromethene ligands and their tri- and tetrapyrrole analogues combine the functions of both a chelating agent and a selective fluorescent sensor of zinc ions compared to other metal ions. Dipyrromethenes and their derivatives demonstrate weak fluorescence whereas metal coordination improves the systems rigidity, which results in fluorescence enhancement. The action of dipyrromethene sensors based on fluorescence buildup effects upon complexation (chelation enhanced fluorescence, CHEF). Fluorescent response of dipyrromethene dye complexation reactions with metal ions can be observed with naked eye. Moreover, the sensors with emissions in the IR region (>650 nm) may be suitable for biochemical applications.

The results of research on the correlation between molecular structure and spectral luminescent and photophysical properties for a new class of dyes and luminophores based on dipyrrins, bis(dipyrrins), and their coordination compounds in different media are summarized. The new perspective applications of dipyrrin dyes and luminophores as fluorescent sensors for measuring the polarity, viscosity, and temperature of the medium and highly sensitive and selective fluorescent “off-on” chemosensors for detecting Zn2+, Cd2+, and Hg2+ cations in weakly polar and nonpolar organic solvents and biological systems are discussed.

3,3',5,5'-Tetraphenyl-2,2'-dipyrromethene was described as a highly sensitive and selective Off-on fluorescent colorimetric chemosensor for Zn2+ based on the chelation-enhanced fluorescence (CHEF) effect. The reaction of dipyrromethene ligand with Zn2+ induces the formation of the [ZnL2] complex, which exhibits the increasing fluorescence in 120 fold compared with ligand in the propanol-1/cyclohexane (1:30) binary mixture. The Zn2+ detection limit was 1.4 × 10-7 М. The UV-Vis and fluorescence spectroscopic studies demonstrated that the dipyrromethene sensor was highly selective toward Zn2+ cations over other metal ions (Na+, Mg2+, Co2+, Ni2+, Fe3+, Cu2+, Mn2+, Cd2+ and Pb2+), excluding Hg2+.

Optical properties of some boron dipyrromethene difluoro (III) (BF2-dipyrromethene) derivatives are studied depending on the ligand structure, the medium in which they are incorporated, irradiation time, and radiation wavelength. Prospects for application of the prepared solid-state media painted by the examined compounds in various optical devices used in modern technologies are demonstrated. These are active laser media in the range 550–565 nm based on three-component silicate matrices with high laser damage threshold and sensor media based on boron difluoride complexes of halogen-substituted dipyrromethenes incorporated into an organic polymer for the determination of oxygen concentration in a gas mixture. Spectral, energy, and resource characteristics of lasing of solid-state elements are presented. The effect of reversible dye photounpainting in three-component silicate matrices with subsequent restoration in the darkness is discovered. Possible reasons for this effect are discussed with allowance for which laser media with increased photostability can be prepared. A high sensitivity of the sensor medium based on diiodinated complex of BF2-dipyrromethene incorporated into polyvinyl butyral is obtained. Reasons for the increase in the response time to the change of the gas mixture when going over to neutral argon and possibilities of its elimination are discussed.

The crystal solvates of 2,2′-, 2,3′- and 3,3′-bis(dipyrrinato)zinc(II) with acetone, dimethyl sulfoxide, and triethylamine were obtained by slow crystallization. Composition, stability, and spectral luminescent properties of the samples were studied. Spectroscopic studies showed that the quantum yield (φ) of crystal solvates in cyclohexane is noticeably lower (to ~1.5–4.5 times) than φ for of [Zn2 L 2] helicates. The thermal dissociation processes of crystal solvates in an argon atmosphere have been investigated. It is shown that bis(dipyrrinato)zinc(II) form stable supramolecular complexes with electron donor molecules X of the composition [Zn2 L 2Xn], where n = 1, 2, or 4. Crystal solvates are stable up to a temperature ~356.9–412.2 К. The energy stability of the solvates [Zn2 L 2Xn] reduced at replacing the 2,2′-bis(dipyrrine) on 2,3′- and 3,3′-isomer and with a decrease in electron donor number of molecular ligands X: Acet, DMSO, TEA. It is demonstrated that the high energies of the coordination interactions Zn–X in supramolecular complexes [Zn2 L 2Xn] are the main cause of the fluorescence quenching of [Zn2 L 2] luminophores in the presence of electron donor ligands X. The obtained results are of interest for the development on the basis of [Zn2 L 2] of the new fluorescent sensors of the electron donor molecules.

Density functional theory (DFT) and Time-dependent density functional theory (TD– DFT) computations have been used to reveal structural, molecular, electronic and spectral–luminescent parameters and features of several homoleptic transition metals bis(dipyrrine) complexes. The influence of complexing agent and ligand nature on the regularities in geometric, spectral–luminescent properties, kinetic and thermal stability changes in the [M2L2] complexes series were studied. Special attention is paid to the influence of the solvating media (PCM/TD–B3LYP/Def2–SVP) on changing spectral–luminescent properties of d-metals bis(dipyrrinate)s. The interpretation of the dependence between spectral–luminescent properties of the complexes and HOMO–LUMO (highest occupied molecular orbital and lowest unoccupied molecular orbital) energy gap's width was given. It was shown that the regularities in changing the helicates’ quantum yield depending on the nature of complexing agent, ligand and solvent properties, obtained from quantum-chemical calculations, are in the agreement with our previously obtained experimental data. Thus, structural and spectral–luminescent characteristics of new [M2L2] luminophors can be evaluated with high reliability, and good forecast prospects for their use as fluorescent dyes for optical devices can be made in terms of the results of theoretical studies (B3LYP/Def2–SVP and TD–B3LYP/Def2–SVP).

The results of studies and comparative analysis of thermal properties and photostability of zinc(II) complexes with tetramethyl- and tetraphenyl-substituted dipyrrins and tetraphenyl-meso-azadipyrrin are reported. The thermal decomposition of complexes starts in the temperature range between 293 and 481°C depending on the molecular structure. Tetraphenyl-substituted zinc(II) dipyrrinate shows the highest photoand thermal stability. The substitution of phenyl moieties in the ligand structure with methyl groups and replacement of the methine spacer with a nitrogen atom reduces thermal stability and photostability of the complexes.

4-Iodo-, 4,4′-, and 5,5′-dibromo-substituted BF2-dipyrrinates (BODIPY) have been prepared, and their spectral luminescent properties and photostability have been studied. It has been shown that the introduction of iodine and bromine atoms in the molecule structure results in build-up of the BODIPY phosphorescence and decrease in their fluorescence quantum yield. Basing on the obtained data, the prepared dipyrrinates can be recommended for development of fluorescent sensors for medical and technical applications.

In this paper, we continue the study of non-covalent supramolecular systems based on zinc bis(dipyrromethenate)s ([Zn2L2]) with fullerene C60 and present the results of study of [Zn2L2]s periphery methylation degree effect on their supramolecular complexation with C60. The structural organization and spectral properties of supramolecular systems based on [Zn2L2]s and C60 were studied by means of UV/vis, fluorescence, time-resolved fluorescence, elemental analysis, FT-IR, PXRD, 1H NMR, DOSY spectroscopy, and computer modeling. The revealed features and the photoelectrochemical characteristics (photocurrent density, IPCE) obtained by the amperometric method give evidence of potential usage of [Zn2L2]s-C60 supramolecular complexes with 1:4 stoichiometry as optoelectronics and photovoltaic devices components.

A fluorescent biomarker based on the boron(III) complex with meso-4-methoxycarbonylbutyl-substituted 3,3',5,5'-tetramethyl-2,2′-dipyrromethene (BODIPY) was synthesized. The BODIPY exhibits a large extinction coefficient (lgɛ ∼4.82–5.00) at 496–501 nm and high fluorescence quantum yield (∼77–100%) in the blue-green region of the spectrum (509–518 nm). The maximal fluorescence quantum yield (φ) is observed in non-polar media (∼100%) while φ slightly decreases to ∼90% in alcohols (with the exception of octanol-1) and to ∼77% in electron-donating dimethyl sulfoxide (DMSO). The BODIPY fluorophore demonstrates high photostability with the half-life of 41.4 and 91 hours in toluene and cyclohexane, respectively. The proposed luminophore preferentially stains gram-positive bacteria and can be used for differential staining of gram-positive and gram-negative bacteria in mixed cultures. BODIPY also accumulates in the cytoplasm of the mammalian cells giving polar micro-speckled staining pattern which is more intensive in the tumor cells when compared to the fibroblasts. The pronounced affinity of BODIPY to mitochondria of eukaryotic cells could be used for specific staining of these organelles.

This paper is a follow-up to our recent study of the zinc(II) bis(dipyrromethenate)s ([Zn2L2]s) sensory capabilities for furosemide detection. We complement our studies with the results of torasemide fluorescent detection by [Zn2L2]s with 0.037–0.11 μg mL−1 detection limit in organic media. The fluorescent sensory materials based on ethyl cellulose doped with [Zn2(1)2] have been developed. It has been shown that ones have high sensitivity to the loop diuretics presence (in 1-propanol the furosemide detection limit is 24 μg mL−1, while torasemide detection limit is 43 μg mL−1). The sensory materials were successfully used for loop diuretics detecting in human urine samples. The results show the loop diuretics detection using [Zn2L2]s and fluorescent sensory materials based on them to be a simple and highly sensitive method of ones detection in organic media and human urine.

In this paper the synthesis and spectral properties of three new dimeric bis(BODIPY)s with two indacene domains connected by a methylene (-CH

The influence of BODIPYs alkylation on the spectral properties in different polarity solvents, PMMA, Langmuir-Schaefer films was studied. The BODIPYs exhibit intense absorption and fluorescence in different nature solvents and PMMA films. The aggregation behavior of BODIPY in Langmuir–Schaefer films was studied. The interaction process of BODIPYs with BSA has been investigated by the multi-spectroscopic approach and molecular docking. It was found that under the selected conditions, the BODIPYs form stable supramolecular systems with BSA due to the prevailing specific interactions. For BODIPY - BSA systems, an increase in the length of 2,6-alkyl radicals in the BODIPY core is accompanied by an increase of the FRET efficiency. This leads to fluorescence enhancement of BODIPYs in the BSA presence. The possibilities of using BODIPYs for labeling hydrophobic regions of blood plasma proteins and biological objects visualization were substantiated.

The spectral luminescent, photophysical, photochemical, lasing, nonlinear optical, and sensor characteristics of a series of new synthesized complexes of zinc and difluoroborate with dipyrrines of different structure have been studied. It is found that many of these compounds exhibit stimulated emission in different solvents when excited by the second (532 nm) and third (355 nm) harmonics of a Nd:YAG laser in the range of 548–692 nm. It is shown that not only efficient fluorophores belonging to dipyrrine difluoroborates (with a quantum fluorescence yield close to 1), but also compounds with a fluorescence yield equal to 0.3, generate laser radiation with a high resource; phosphorescence is also observed along with fluorescence. Transmission of UV radiation (355 nm) is shown to decrease with an increase in the pulsed excitation power density; this is a manifestation of nonlinear optical properties. The change of phosphorescence signal in dependence of the composition of the gas mixture around a solid-state sample colored by dipyrrinate complexes indicates that a number of the compounds under consideration exhibit sensor abilities.

Crystal solvates of 2,2′-, 2,3′- and 3,3′-bis(dipyrrinato)zinc(II) with triethylamine (TEA) were obtained by slow crystallization. Composition, structural organization, stability, and spectral-luminescent properties of the crystal solvates were studied by FTIR, Powder X-ray Diffraction, thermal, mass spectral, absorption and fluorescence analyses. The thermal dissociation processes of crystal solvates in an argon atmosphere have been investigated. It is shown that zinc(II) helicates with decamethylsubstituted 2,2′-, 2,3′-, and 3,3′-bis(dipyrrin)s with TEA form stable supramolecular complexes of the composition [Zn2L2(TEA)4] and [Zn2L2TEA]. Spectroscopic studies showed that the quantum yield (φ) of [Zn2L2(TEA)n] crystal solvates in cyclohexane is noticeably (3–4.5 times) lower than φ of [Zn2L2] complexes. Quantum chemical study indicated the most likely mechanism for the coordination of solvent molecules on the coordinating centers of [Zn2L2]. Thermal and energy stability of [Zn2L2(TEA)n] solvates ...

This paper presents the results of quantum-chemical and spectral studies on studying fluorescence of binuclear zinc(II)–bis(dipyrrinate)s [Zn2L2] in non-polar and polar environments and their binary mixtures. We studied the efficiency of the fluorescence quenching of fluorophores depending on of isomerism forming their bis(dipyrrine) ligands and an electron-donating ability of the solvent. Found that 3,3′-bis(dipyrrinato)zinc(II) demonstrates the highest sensitivity of the fluorescence to the presence of the electron-donor component compared with 2,3′- and 2,2′-analogs. The results obtained allow to offer helicates [Zn2L2] as new, highly sensitive and selective fluorescent sensors for the detection of N- and O-containing analytes.

New polymeric materials containing dinuclear double-stranded zinc(II) helicate with bis(1,2,3,7,9-pentamethyldipyrrin-8-yl)methane have been prepared on the basis of poly(methyl methacrylate) and tetraethoxysilane. The zinc(II) complex [Zn2L2] retains its fluorescence properties in a poly(methyl methacrylate) film. The photostability of [Zn2L2] in poly(methyl methacrylate) is higher by a factor of ≈2.5 than in the benzene solution. Conditions have been found for the preparation of [Zn2L2]-doped silicate matrix based on tetraethoxysilane via the sol–gel method. The [Zn2L2] complex in the tetraethoxysilane solid matrix shows a weak fluorescence with its maximum at λ = 545–549 nm.

Synthesis, spectral-luminescence properties of the zinc(II)–dipyrrinates containing one or two I- and Br-atoms at the pyrrole rings are described. We have studied the changes of the spectral-luminescent properties of zinc(II) complexes with iodo- and bromosubstituted 2,2′-dipyrrines depending on the characteristics of their molecular structure and properties of the medium. The results obtained provide the potential use of halogenated zinc(II)–dipyrrinates in developing fluorescent dyes for engineering and medical applications.

The geometric parameters of the molecular structures of 4-monoiododipyrrine, 4,4′- and 5,5′-dibromodipyrrine complexes with zinc(II) and boron(III) of the composition [ZnL2] and [BF2L] respectively are determined at the M06 and B3LYP levels of density functional theory with the Def2-SVP basis set. The lengths of Zn–N, B–N, and B–F coordination bonds, N–X–N, F–B–F, C–C–C bond angles, the dihedral angles between the planes of pyrrole rings in the dipyrrine ligand, dipyrrine planes in [ZnL2], dipyrrine core and the plane passing through the atoms of the BF2 group are optimized. The effect of structural factors on the geometric parameters and the widths of the HOMO–LUMO energy gap in halogen substituted dipyrrinates is analyzed.

Boron(III) complexes with phenyl-substituted meso-aza-dipyrromethenes (one of them 4,4'-brominated) have been prepared. The bromination has resulted in weakening of the compound fluorescence by more than ten-fold. The studied complexes are stable for a long time in the solutions in non-polar solvents both in the dark and exposed to light. The bromine-containing complex rapidly decomposes in the polar media.

New “off-on” Zn2+ fluorescent probes in organic solvents were developed underlain by ligands consisting of deca-, octa-, and tetramethyl-substituted 3,3′-bis(dipyrrins). The coordination of the probes with two Zn2+ ions with the formation of complexes [Zn2L2] is accompanied with a significant (200–550-fold) increase in the fluorescence intensity. The fluorescence response is maximum for the reaction of Zn2+ with tetramethyl-substituted 3,3′-bis(dipyrrin). The presence of cations of Na+, Mg2+, Mn2+, Co2+, Ni2+, Cd2+, Hg2+, and other metals, save Cu2+, does not interfere with the detection of Zn2+ demonstrating the high selectivity of bis(dipyrrin) Zn2+-sensors.

This microreview covers the currently available data about the synthesis and practically valuable spectral and luminescence properties of tetraaryl-substituted aza-BODIPY dyes.

In this paper, we report on the results of spectrofluorimetric study of new fluorescent sensor based on [Zn2L2] doped in ethyl cellulose. The sensor optical signal is based on the rapid fluorescence quenching in the presence of acetone vapor. The acetone vapor detection limit in a gas mixture by means of sensor based on [Zn2L2] doped in ethyl cellulose is 1.68 ppb. Being highly sensitive to the acetone acetone presence, instant in response and easy to use, the sensor can find an application for the noninvasive diagnostics of diabetes as well as for the monitoring of the content of acetone acetone in the air at industrial and laboratory facilities.

In the present paper spectral–luminescent, lasing, photochemical, sensory, and photosensitized characteristics of a number of Zn(II) and B(III) coordination complexes of dipyrrins with different structures are investigated. The results show that alkyl-, phenyl-, and propargylamino-derivatives of dipyrrin core in these complexes have excellent luminescent characteristics and can be used as active media for tunable liquid and solid-state lasers. Zinc (Zn-dpm 2 ) and boron fluoride complexes of dipyrrins (BODIPYs) with halogen atoms and aza-substitution in meso- position in their ligands do not exhibit effective fluorescence, but some of them have long-lived emission due to increased nonradiative intersystem processes in an excited state proceeding by the mechanism of heavy atom and the presence of low-lying nπ- and σπ-states of different natures and multiplicities. The reason for the short-wavelength shift of the Zn-dpm 2 spectra compared to the corresponding BODIPY is studied using quantum-chemical calculation. For solid samples based on halogenated complexes, a dependence of the long-lived emission intensity on the oxygen concentration in the surrounding gas mixture is established that indicates the possibility of application of these complexes for the creation of optical oxygen sensors. Moreover, results of investigations of halogen-substituted tetraphenyl-aza-BODIPY complexes as photosensitizers of singlet oxygen production are presented. Such complexes are promising for creating media for generation of singlet oxygen, which is important for photodynamic therapy and oxidation catalysis. In addition, data on the stability of these compounds in different electronic states are presented.

The constants of acid-base equilibrium were estimated with spectroscopic method at the ground (S0) and at the fluorescent (S1fl) states. The constants of acid-base equilibrium for Franck-Condon excited states (S1F-C) were estimated from spectral shifts for basic and acid forms. This results are compared with quantum yields of photostability of complexes in neutral solvents. The mechanisms of complexes protonation are discussed dependence from the structure of ligands.

The review highlights recent advances devoted to new luminophores based on d -metal complexes of bis(dipyrrin)s of [M 2 L 2 ]. The [M 2 L 2 ] helicates possess intense absorption in a visible spectrum region. The [Zn 2 L 2 ], [Cd 2 L 2 ] and [Hg 2 L 2 ] helicates are fluorophores with the most intense fluorescence in nonpolar solvents. The fluorescence of [M 2 L 2 ] bis(dipyrrinate)s decreases by two-fold in aromatic solvents and becomes close to zero in electron-donor media. The fluorescence is increased in a series of 2,2′-, 2,3′-, 3,3′-bis(dipyrrinate)s with similar complexing agent and in a series of [Hg 2 L 2 ], [Cd 2 L 2 ], [Zn 2 L 2 ] complexes with the same ligand. Upon freezing and cooling of [Zn 2 L 2 ] in ethanol from 300 to 77 K the fluorescence quantum yield of [Zn 2 L 2 ] is increased up to 100 times. The [Zn 2 L 2 ] complexes are able to generate the stimulated emission induced at the 550–560 nm region in nonpolar solvents upon excitation by second harmonic Nd:YAG laser.

The boron-dipyrromethene (BODIPY) dye containing an annelated cyclohexyl rings at the 2,3 and 5,6-positions of pyrroles has been synthesized and characterized. Photochemical properties of the obtained compound have been investigated in different individual solvents. 2,3;5,6-Bis(cyclohexano)-BODIPY exhibits intense chromophore properties with maximum of S o → S 1 band in the 543–549 nm (A from 66000 to 96000 L/mol·cm). The complex is a fluorophore with a quantum yield up to ~ 100%. The influence of solvent polarity on the spectral properties was evaluated. To better understand the spectroscopic results, quantum chemical calculations were carried out. Photostability of dye was studied. Graphical Abstract

The results of investigation of the spectral characteristics, photostability and thermal degradation of B(III) and Zn(II) complexes with 3,3′,5,5′-tetramethyl-2,2′-dipyrromethene and meso-phenyl-3,3',5,5′-tetramethyl-2,2′-dipyrromethene were presented. It has been shown that meso-phenyl substitution in the 3,3′, 5,5′-tetramethyl-2,2′-dipyrromethene complexes with B(III) and Zn(II) leads to a hypsochromic displacement S0 → S1 bands in the EAS and a significant increase in its intensity, but a decrease in the fluorescence quantum yield. It has been established that the introduction of phenyl substituent in the meso-position causes an increase in thermal stability (up to 20 °C in Bodipy and up to 74 °C in Zn-complexes) and photostability (up to 3 times for Bodipy and up to 7 times for Zn(II) dipyrromethenates).

A comparative study of spectral, luminescent, and photophysical parameters has been carried out for a series of zinc(II) and boron(III) chelates with dipyrromethene ligands of a similar structure: tetramethyl- and tetraphenylpyrrodimethenes bearing the substituents on the pyrrole rings and tetraphenylazapyromethene. In some cases, the luminescence efficiency of the chelates depends on the excitation wavelength. The replacement of the central atom boron(III) by zinc(II) results in not only a twofold increase in the number of coordinated chromophoric ligands and the absorption coefficient, but also an increase in the contribution of nonradiative processes to excitation energy deactivation and, hence, a decrease in the yield of fluorescence. The efficiency of intersystem crossing is higher in the zinc(II) dipyrromethene complexes than in the corresponding boron-chelated dipyrromethenes (BODIPYs), resulting in the appearance of phosphorescence in frozen solutions. It has been found that the replacement of the meso-spacer in the dipyrromethene ligand by the nitrogen atom not only shifts the absorption and fluorescence band maximums to longer wavelengths, but also decreases the fluorescence efficiency and leads to the appearance of long-lived luminescence even in aza-BODIPY. An analysis of the results has shown that these behavior can be due to involvement of the nπ* (πσ*, σπ*) states localized on the meso-nitrogen in the deactivation of excitation energy.

The crystal structure of the boron(III) complex [BF2L] synthesized for the first time, where L− is the 3,3′,5,5′-tetramethyl-4-ethyl-4′-iododipyrrolylmethene-2,2′ monoanion (iodo-BODIPY, monoclinic crystals: a = 12.0329(6) A, b = 15.9657(8) A, c = 8.5080(4) A, β = 103.753(1)°, V = 1587.64(13) A3, Z = 4 (Z′ = 1), space group P21/c) is determined. In the structure, two pyrrol rings and the central six-membered ring containing a boron atom are in one plane, perpendicular to which a plane formed by a group of F-B-F atoms is located. The crystal packing is formed by van der Waals interactions. In the electron absorption spectra of iodo-BODIPY solutions in nonpolar solvents, unlike polar ones, a red shift up to 3–8 nm of the maximum of the first intense band is observed, for which the lgɛ value reaches ∼4.71. Along with intense chromophoric properties, the synthesized iodo-BODIPY complex is a sufficiently strong fluorophore and can be used as a fluorescent marker.

The surface of silica particles was modified with polyvinyl pyrrolidone (PVP) through solegel process. The different experimental techniques, i.e., thermogravimetric analysis (TGA and DTG), nitrogen adsorption, scanning electron microscopy (SEM), laser diffraction analysis (LDA), fourier transform spectroscopy (FTIR) are used to characterize the pure non-functionalized and functionalized silicas containing different amount of PVP. It was shown that PVP-modified silica samples have well developed porous structure; the values of specific surface area for PVP-modified silicas are in the range of 140 e264 m 2 g � 1 . While the non-functionalized silica shows the low surface area (S BET ¼ 40 m 2 g � 1 ). The BJH analysis showed that PVP can be used as an effective agent to increase an average pore size and total pore volume. The results indicate that PVP functionalized silicas show a potential as effective adsorbents for bilirubin removal compared to other available adsorbents.

Effect of complexing atom, molecular structure of dipyrrolylmethene and its aza analog on spectral-luminescent properties of heteroleptic boron(III) and homoleptic zinc(II) complexes with 3,3′,5,5′-tetramethyl-2,2′-dipyrrolylmethene, 3,3′,5,5′-tetraphenyl-2,2′-dipyrrolylmethene, and 3,3′,5,5′-tetraphenyl-ms-aza-2,2′-dipyrrolylmethene in organic solvent solutions was studied. The complexes were found to exhibit strong chromophore (λ = 350–690 nm, ɛ ∼ 105 L/mol cm) and fluorescent properties. Quantum yield (γfl) for fluoroborate complexes reaches 100% and is weakly dependent on medium nature. The value of γfl for phenyl- and alkyl-substituted zinc(II) dipyrrolylmethenates in nonpolar solvents is not higher 0.3 and 0.03, respectively; complete fluorescence quenching is observed in electron-donating solvents. Aza-substitution at the meso spacer causes considerable shift of electronic absorption and fluorescence spectra to the red region but completely quenches fluorescence of zinc(II) chelates and decreases γfl of boron(III) complex to 0.04.

Emission spectra of diiodine-substituted boron dipyrromethene (I2BODIPY) dye in ethanol solutions and in methylcellulose matrix were studied. The solid patterns were photoexcited at 520 nm and display room temperature phosphorescence with a maximum at 790 nm that is quenched by molecular oxygen at room temperature. Novel sensing material for oxygen concentration detection from 0% to 100% has been developed on the basis of I2BODIPY with 17-fold sensitivity (IAr/IO2), reverse, fast response (1 s) and linear calibration. The sensitivity dependence on the active substance concentration in matrix was shown.

A kinetic model and a mechanism have been developed by quantum chemical simulation for the protolytic dissociation of dinuclear homoleptic bis(dipyrrolylmethenates) of d-metals (M) with the general formula [M2L2] and a double-helix structure. The reaction is described by a third-order equation that is first-order with respect to the complex and second-order with respect to the acid. The main contribution to the total dissociation rate is made by the rate-determining step, specifically, attack of the second acetic acid molecule on the nitrogen atom of one of the coordination sites of the helicate. The dinuclear helicates of 3,3′-bis(dipyrrolylmethenes) are more inert in an acidic medium than 2,3′- and 2,2′-bis(dipyrrolylmethenes).

The effect of the attachment position of a methylene spacer in 2,2′-, 2,3′-, and 3,3′-bis(dipyrromethene) N4-ligands (H2L) on physicochemical properties of their dinuclear homoleptic helicates [Zn2L2], such as specific features of their molecular structure, luminescence spectral characteristics, lability in acid solutions, and thermal stability in an argon atmosphere, has been examined. It has been shown that the substitution of the biladiene-type helicand by its 2,3- and especially 3,3′-analogues leads to a considerable enhancement of the chromophoric properties, an increase (up to 30-fold) of the fluorescence quantum yield, and an increase in the stability of corresponding dinuclear helicates [Zn2L2].

Quantum chemical calculations of the molecular structure of bis(dipyrrolylmethanates) of cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), and mercury(II) of the composition [M2L2] are performed using the PM6 method within the Gaussian 09W program package. The lengths of M-N coordination bonds, the values of dihedral angles formed by N-M-N bonds, the distances lM⋯M between the M⋯M atoms are optimized. It is noted that the regularities obtained from the analysis of the results of quantum chemical calculations of the molecular structure of [M2L2] helicates reliably reflect the main trends of changes in their physicochemical properties depending on the nature of a complexing agent and the features of the ligand structure.

The complex formation of indium(III) acetate with tetra-, octa- and decamethyl-substituted 3,3′-bis(dipyrromethene)s (H2L) in DMF (298.15 K) was studied by means of spectrophotometric titration. For the first time, the most probable mechanism of the complexation process of indium(III) with bis(dipyrromethene) ligands was proposed, taking into account the role of the solvating medium. It was found that the coordination process of the H2L ligands by the In3+ ions includes the successive stages of the formation of intermediate mono- and binuclear heteroligand complexes of the compositions [In(AcO)2HL], [(In(AcO)2)2L] and [(InAcO)2L2] and of the final most of a stable binuclear triple-helix helicate of composition [In2L3]. It was established that the effect of the methylation features of bis(dipyrromethene) ligands manifests itself in a significant increase (~1.4–1.7 times) of the complexation processes thermodynamic constants logarithms (lgКo) for [In2L3] helicates with unsubstituted α-positions of the terminal pyrrole rings of ligands compared to completely methylated analogue. It is shown that the ligands of 3,3′-bis(dipyrrometene)s can be recommended as new effective highly sensitive “naked eye” sensors of trace amounts (up to ~31·0−7 mol/l) of In3+ cations in organic media.

In this paper, the sensitivity of new fluorescent sensors based on zinc(II) bis(dipyrromethenate)s ([Zn2L2]s) to the furosemide presence in organic media is described. It has been shown that the instantaneous spectral response of [Zn2L2]s to the furosemide presence is based on the fluorescence quenching effect. Multi-approach analysis (UV–vis and fluorescent titrations, PXRD, FTIR, 1H NMR, DOSY, and DFT calculations) has shown that the [Zn2L2]s fluorescence quenching is associated with the formation of stable [Zn2L2Fur]s supramolecular systems, capable of photoinduced electron transfer. The furosemide detection limit with using [Zn2L2]s was 65–78 μg L−1. The proposed sensors can be used for the forensic, clinical and sports medicine needs.

The luminescence-spectral, lasing and photochemical characteristics of laser media based on boron fluoride complexes of dipyrromethenes, embedded into solid bulk matrices of polymethylmethacrylate and its modifications (obtained by adding polyhedral oligomeric silsesquioxane during polymerisation) and into polymer films, in which polyhedral silsesquioxane enters the composition of monomeric unit, have been investigated.

Using fluorescence and electronic spectroscopy the interaction of boron-dipyrromethene complex (BODIPY) with bovine serum albumin (BSA) and its bilirubin macromolecular complex (BR·BSA) in aqueous solution was investigated. The interaction of BODIPY is carried out by the static quenching of protein fluorescence and is predominantly hydrophobic and electrostatic in nature. The values of the binding constants were (61.2 ± 2.8) · 103 and (6.51 ± 0.3) · 103 M−1. The interaction of BODIPY with proteins leads to the observed hypso- and bathochromic shift in BODIPY absorption band. Forster resonance energy transfer theory allowed of determing the donor-ligand distance, which were 2.88 and 2.46 nm for BSA and BR·BSA, respectively. Using synchronous fluorescence spectroscopy it was possible to reveal features of BODIPY influence on conformational changes in protein molecules. It was established that BODIPY more effectively interacts with BSA compared to BR·BSA.

Luminescence study of the reaction of 3,3′-methanediylbis(2,4,7,8,9-pentamethyldipyrrolylmethene) (H2L) with a number of metal salts showed that this compound is an efficient fluorescent chemosensor for Zn2+ ions in organic solvents. The selectivity and sensitivity of H2L were estimated in various solvents in the presence of other metal cations (Na+, Mg2+, Co2+, Ni2+, Cu2+, Cd2+, Hg2+, Pb2+).

We have studied the spectral-luminescent, lasing, photochemical, and endurance characteristics of a series of new efficiently emitting difluorine borate complexes with dipyrrolylmethenes of different structures. Experimental data have been obtained in polar and nonpolar organic solvents and in solid polymer films involving the participation of silicate structures. We have discussed relations of the structure of investigated compounds and formed solvates with their optical characteristics, and have given guidelines on the use of particular compounds as active media of tunable lasers for determining spectral ranges.

Protolytic dissociation of copper(II) and nickel(II) dipyrrolylmethenates in benzene solutions of acetic acid has been studied. The results have completed the knowledge of kinetics of dipyrrolylmethene complexes dissociation in acidic medium. The effect of the nature of complex forming atom, ligand, and other factors on the complexes kinetic stability has been analyzed.

The interactions of bovine serum albumin (BSA) and its bilirubin (BR) macromolecular complex (BR·BSA) with meso-tetrakis-(p-sulfophenyl)porphin (TSPP) have been studied by electronic spectroscopy, and emission and synchronous fluorescence in phosphate buffer at pH 7.4. The parameters of the resulting intermolecular complexes (binding constants, quenching rate constants, etc.) were established. The values of the binding constants for the BSA–TSPP and BR·BSA–TSPP systems were 13 × 104 and 8.0 × 104 dm3 mol−1, respectively. The interaction of TSPP with the proteins is studied by static quenching of protein fluorescence, showing predominantly hydrophobic and electrostatic nature. During the complex-formation process, a bathochromic shift of the TSPP Soret band occurs. The influence of TSPP on conformational changes of the protein molecules was analyzed using synchronous fluorescence spectroscopy. It was found that there is competition of BR with TSPP for binding sites on the protein, resulting in displacement of BR from the complex. .

A fluorescent chemosensor based on the 3,3'-bis(dipyrrin) bearing two chromophoric dipyrrin units was synthesized, which showed a strongly enhanced fluorescent intensity in the presence of Zn(2+) ions and a high selectivity toward Zn(2+) ions over a wide range of tested metal ions in organic solvents.

Complexes [ML2] of cobalt(II), nickel(II), copper(II), zinc(II), and cadmium(II) with asymmetrically substituted (E)-3-ethyl-5-[(4-iodo-3,5-dimethyl-2H-pyrrol-2-ylidene)methyl]-2,4-dimethyl-1H-pyrrole (HL) have been prepared and characterized for the first time. The spectral properties, stability in solutions and in the solid phase at elevated temperature of the complexes have been studied. The effects of complexing metal ion and the reaction medium on the spectral luminescent properties (absorptivity, quantum yield, fluorescence lifetime, and the radiation constant) and on thermal destruction of the [ML2] complexes have been discussed.

The study and comparative analysis of spectral-luminescent characteristics (absorption and fluorescence spectra), of quantum yield, and fluorescence life time in solutions, of lability in proton-donor media, solid phase thermal stability in air oxygen and argon was carried out for binuclear zinc(II) helicates with decamethyl-substituted 2,3′- and 3,3′-bis(dipyrrolylmethenes). The influence of molecular structure features of the ligands on the physicochemical properties of helicates was discussed.

The trends of kinetic resistance of borofluoride complexes of alkyl- and sulfo-substituted dipyrrolylmethene (Bodipy) to protolytic and solvoprotolytic dissociation in organic solvents and aqueous solutions are studied. It is established that among dipyrrolylmethene complexes with d elements, Bodipy is notable for its superresistance to acids. The rate of the dissociation reaction increases with increasing acidity of protonating mixtures or decreasing effective charge of the coordinating nitrogen atoms of the ligand. Dissociation of the complexes occurs in accordance with a second-order rate equation. A kinetic model of the process is proposed; its kinetic and activation parameters are determined. The energy profiles of the initial stages of protolytic dissociation reactions are calculated using quantum-chemical methods for two suggested variants of the transient state; the energetically preferable pathway is recognized.

Using spectrophotometry we found that ligand exchange in the systems of H2L-[MX2]-DMF, where M denotes Co2+, Cu2+, and Zn2+; X means Acac−, Val−, dpm−; Hdpm− is hexamethyldipyrrolylmethene, H2L is bis(2,4,7,8,9-pentamethyldipyrrolylmethene-3-yl)methane, proceeds through successive stages of formation of hetero- and homoleptic binuclear complexes. Conventional sensitivity of the spectrophotometric determination of Co2+, Cu2+, and Zn2+ reaches 10−9 M.