Protonation of some non-transition metal phthalocyanines — spectral and photophysicochemical consequences

Ogunsipe, Abimbola; Idowu, Mopelola Abidemi; Ogunbayo, Taofeek B.; Akinbulu, Isaac Adebayo

doi:10.1142/s1088424612500988

Cited by 19 publications

(7 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In accordance with literature reports, protonation of the azomethine nitrogen atoms was accompanied by a significant decrease in fluorescence . The Φ F values of the azomethine‐protonated species dropped to zero, indicating that this quenching process is extremely efficient.…”

Section: Resultssupporting

confidence: 92%

“…Thus, strong fluorescence is expected only at intermediate pH values, leading to a narrow pH‐sensing window. Notably, protonation of the azomethine nitrogen atom has been mentioned in the literature as leading to a substantial decrease in the fluorescence quantum yields of both Pcs and TPyzPzs, but has seemingly never been used as a concept in molecular switches or logic gates.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

OFF‐ON‐OFF Red‐Emitting Fluorescent Indicators for a Narrow pH Window

Cidlina

Miletín

Fathi-Rasekh

et al. 2016

Chemistry A European J

View full text Add to dashboard Cite

A unique combination of two independent mechanisms of fluorescence quenching, namely intramolecular charge transfer (ICT) from a peripheral donor and protonation of azomethine nitrogen atoms in zinc tetrapyrazinoporphyrazines (TPyzPz), provides a new possibility for sensing pH in a specific range. The pH selectivity was controlled by the different basicities of the donor for ICT (dimethylaminoaryl), which was connected to the macrocycle by π-extended linkers of different lengths. ICT and protonation have been studied in detail by photophysical, spectral (UV/Vis and MCD spectra), and electrochemical measurements, and further supported by theoretical calculations (DFT, TDDFT). The pH-sensing properties of the TPyzPzs have been investigated in THF and in water after anchoring the TPyzPzs to liposomes. The salient pK values were around 1.3 (azomethine nitrogen) and 2.29-4.76 (donor for ICT). The lead indicators (sensing over a pH range of 1.0-2.5) with fairly steep sensing profiles exhibited increases in fluorescence between the OFF/ON states of more than 20-fold and strong absorption in the red region (Q-band maximum >650 nm, ϵ≈2×10 m cm ).

show abstract

Section: Resultssupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

OFF‐ON‐OFF Red‐Emitting Fluorescent Indicators for a Narrow pH Window

Cidlina

Miletín

Fathi-Rasekh

et al. 2016

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…The green color is due to the addition of a blue dye solution to a slightly yellow-colored sol, resulting from addition of the ammonia solution. The spectra recorded after addition of dye solution to sols confirmed the presence of zinc phthalocyanine in the analyzed system [24][25][26]. The series of protic solvents were used for sol-gel synthesis to develop influence of the acidic character of alcohols.…”

Section: Uv-vis Analyzesmentioning

confidence: 90%

Effect of Solvent and Catalyst Types on Stability and Properties of Zinc Phthalocyanine in the Organic–Inorganic Hybrid Materials

2021

View full text Add to dashboard Cite

Hybrid materials, i.e., the organically modified silicates (ORMOSIL) based on zincphthalocyanine (ZnPc) and silica glass matrix were synthesized by the sol-gel method using protic solvents (methanol, ethanol, isopropanol, butanol) and aprotic solvent (N,N-dimethylformamide; DMF). The effect of an alkaline environment with NaOH addition (a single-stage process) and acid–alkaline environment with CH3COOH-NH4OH and HCl-NaOH (a two-stage process) was analyzed. UV-Vis spectroscopy was used to study the stability of ZnPc in the sol. The highest stability of zinc phthalocyanine in the glass was obtained for synthesis with isopropanol in the presence of the alkaline catalyst. The lowest stability of ZnPc was observed when the aprotic solvent was used. The structure and optical properties of the gels were studied by SEM, FTIR, and XRD techniques and optically stimulated luminescence (OSL) and thermoluminescence (TL), respectively. The thermal stability of the materials was analyzed by TG-DSC methods.

show abstract

“…Basically, the protonated Pc macrocycle is considered less chemically stable [ 23 , 24 , 25 , 26 ]. Notably labile compounds (e.g., PbPc, MgPc) do not create stable protonated forms and are subject to prompt demetallation and subsequent cleavage of the Pc moiety, particularly in the presence of strong acids such as H 2 SO 4 [ 27 , 28 ]. Incidentally, some complexes (NiPc, CuPc) proved to resist even that strong acids, nevertheless several phthalocyanines appeared quite stable in less aggressive protic media, and demonstrated interesting acid-base chemistry [ 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ].…”

Section: Introductionmentioning

confidence: 99%

Hydrogen Bond-Mediated Conjugates Involving Lanthanide Diphthalocyanines and Trifluoroacetic Acid (Lnpc2@TFA): Structure, Photoactivity, and Stability

et al. 2020

View full text Add to dashboard Cite

The interaction between lanthanide diphthalocyanine complexes, LnPc2 (Ln = Nd, Sm, Eu, Gd, Yb, Lu; Pc = C32H16N8, phthalocyanine ligand) and trifluoroacetic acid (TFA) was investigated in benzene, and the stability of the resulting molecular system was assessed based on spectral (UV-Vis) and kinetic measurements. Structural Density Functional Theory (DFT) calculations provided interesting data regarding the nature of the bonding and allowed estimating the interaction energy between the LnPc2 and TFA species. Conjugates are created between the LnPc2 and TFA molecules via hydrogen bonds of moderate strength (>N∙∙H··) at the meso- -bridges of the Pc moieties, which renders the sandwich system to flatten. Attachment of TFA is followed by rearrangement of electronic density within the chromophore system of the macrocycles manifested in considerable changes in their UV-Vis spectra and consequently the color of the studied solutions (from green to orange). The LnPc2@TFA conjugates including Nd, Sm, Eu, and Gd appeared evidently less photostable when exposed to UV radiation than the related mother compounds, whereas in the case of Yb and Lu derivatives some TFA-prompted stabilizing effect was noticed. The conjugates displayed the capacity for singlet oxygen generation in contrast to the LnPc2s itself. Photon upconversion through sensitized triplet–triplet annihilation was demonstrated by the TFA conjugates of Nd, Sm, Eu, and Gd.

show abstract

Protonation of some non-transition metal phthalocyanines — spectral and photophysicochemical consequences

Cited by 19 publications

References 40 publications

OFF‐ON‐OFF Red‐Emitting Fluorescent Indicators for a Narrow pH Window

OFF‐ON‐OFF Red‐Emitting Fluorescent Indicators for a Narrow pH Window

Effect of Solvent and Catalyst Types on Stability and Properties of Zinc Phthalocyanine in the Organic–Inorganic Hybrid Materials

Hydrogen Bond-Mediated Conjugates Involving Lanthanide Diphthalocyanines and Trifluoroacetic Acid (Lnpc2@TFA): Structure, Photoactivity, and Stability

Contact Info

Product

Resources

About