Photochemistry of rhodamine dye salts involving intra-ion-pair electron transfer

2003 ◽  
Vol 81 (6) ◽  
pp. 789-798 ◽  
Author(s):  
Guilford Jones II ◽  
Xiaochun Wang ◽  
Jingqiu Hu
Keyword(s):  
Electron Transfer ◽  
Ethyl Acetate ◽  
Rhodamine 6G ◽  
Radical Pair ◽  
Ion Pairs ◽  
Ion Pair ◽  
Thiocyanate Ion ◽  
Rhodamine Dye ◽  
Triplet Radical Pair ◽  
Pair State

The electron-transfer photochemistry of rhodamine 6G thiocyanate ion pairs has been investigated. For dye in a low polarity solvent, such as ethyl acetate, the emission of rhodamine 6G is significantly quenched by thiocyanate counterions. Laser photolysis of rhodamine 6G and thiocyanate in ethyl acetate was studied in detail with the identification of the reduced rhodamine 6G radical species (λmax = 410 nm). The growth and decay of the R6G radical could be accounted for in part by a mechanism involving initial formation of dye triplet followed by electron transfer which provides a triplet radical-pair state on a µs timescale.Key words: electron transfer, ion pair, rhodamine 6G, triplet state.

scholarly journals The photochemistry of 1-naphthylmethyl carbonates and carbamates

1994 ◽  
Vol 72 (5) ◽  
pp. 1254-1261 ◽  
Author(s):  
T. Parman ◽  
J.A. Pincock ◽  
P.J. Wedge
Keyword(s):  
Electron Transfer ◽  
Singlet State ◽  
Radical Pair ◽  
Ion Pair ◽  
Excited Singlet State ◽  
Excited Singlet ◽  
Homolytic Cleavage ◽  
Product Yields ◽  
Oxygen Bond

The photochemistry in methanol of 1-naphthylmethyl phenyl carbonate (3) and 1-naphthylmethyl benzyl carbonate (4) has been studied. Products resulting from both the 1-naphthylmethyl cation and the 1-naphthylmethyl radical are obtained for 3, but only from the cation for 4. Similar results were obtained for the corresponding 1-naphthylmethyl derivatives 5 and 6 of N-phenyl and N-benzyl carbamic acids. The product yields for all four compounds can be explained by a mechanism of initial homolytic cleavage of the 1-naphthylmethyl carbon–oxygen bond from the excited singlet state. The radical pair generated then partitions between the two pathways: electron transfer to form the ion pair or decarboxylation. For PhO-CO-O• and PhNH-CO-O•, decarboxylation is rapid and competitive with electron transfer. For PhCH2O-CO-O• and PhCH2NH-CO-O•, decarboxylation is slower, electron transfer dominates, and only products from the ion pair are obtained.

Formation of a long-lived radical pair in a Sn(iv) porphyrin–di(l-tyrosinato) conjugate driven by proton-coupled electron-transfer

2018 ◽  
Vol 54 (48) ◽  
pp. 6148-6152 ◽  
Author(s):  
Mirco Natali ◽  
Agnese Amati ◽  
Nicola Demitri ◽  
Elisabetta Iengo
Keyword(s):  
Electron Transfer ◽  
Radical Pair ◽  
Quenching Mechanism ◽  
Proton Coupled Electron Transfer ◽  
Tin Porphyrin ◽  
Pair State

A surprisingly long-lived radical pair state is achieved in a tin-porphyrin/l-tyrosine conjugate by exploiting a photochemical PCET quenching mechanism.

Internal return in the photochemistry of ring-substituted 1-(1-naphthyl)ethyl esters of phenylacetic acid

1995 ◽  
Vol 73 (6) ◽  
pp. 885-895 ◽  
Author(s):  
J.M. Kim ◽  
J.A. Pincock
Keyword(s):  
Electron Transfer ◽  
Transfer Rate ◽  
Experimental Error ◽  
Phenylacetic Acid ◽  
Radical Pair ◽  
Ion Pair ◽  
Ethyl Esters ◽  
Electron Transfer Rate ◽  
Radical Pairs ◽  
Substituted 1

The photochemistry in methanol of the esters 12a–d has been studied in order to determine the importance of internal return of both ion pair and radical pair intermediates. The efficiency of internal return, determined by monitoring 18O exchange between the alcohol and carbonyl oxygens, was shown to be substituent dependent, varying from approximately 10% for the 4,7-dimethoxy substrate to nearly 50% for the 4-cyano case. The corresponding ground state solvolysis reactions gave about 10% internal return and, within experimental error, were substituent independent. Internal return was also examined by racemization of the chiral center in 12a and 12d. In summary, these combined results reveal that internal return probably occurs mainly through a contact (not solvent-separated) radical pair. More important, internal return has little effect on previously calculated electron transfer rate constants for converting the radical pair to the ion pair. Therefore, the previously reported Marcus' correlations are valid. Keywords: photochemistry of benzylic esters, internal return, photosolvolysis, electron transfer, radical pairs.

A Transient EPR Study of Electron Transfer in Tetrathiafulvalene-Aluminum(III) Porphyrin-Anthraquinone Supramolecular Triads

2017 ◽  
Vol 231 (2) ◽  
Author(s):  
Prashanth K. Poddutoori ◽  
Yuri E. Kandrashkin ◽  
Art van der Est
Keyword(s):  
Electron Transfer ◽  
Spin Polarization ◽  
Electron Spin ◽  
Charge Separation ◽  
Radical Pair ◽  
Electron Spin Polarization ◽  
Induced Charge ◽  
Pair State

AbstractThe stabilization of light-induced charge separation in two axially bound triads based on aluminum(III) porphyrin (AlPor) are investigated using the electron spin polarization patterns of the final radical pair state. In the triads, TTF-(Ph)

Stereospecific 1,3-H Transfer of Indenols Proceeds via Persistent Ion-Pairs Anchored By NH···Pi Interactions

2018 ◽  
Author(s):  
David Ascough ◽  
Fernanda Duarte ◽  
Robert Paton
Keyword(s):  
Computational Analysis ◽  
Ion Pairs ◽  
Ion Pair ◽  
Hydrogen Atom Transfer ◽  
Polar Solvents ◽  
Chirality Transfer ◽  
Activation Barriers ◽  
Sense And Avoid ◽  
Phase Dynamics ◽  
Pi Interactions

The base-catalyzed rearrangement of arylindenols is a rare example of a suprafacial [1,3]-hydrogen atom transfer. The mechanism has been proposed to proceed via sequential [1,5]-sigmatropic shifts, which occur in a selective sense and avoid an achiral intermediate. A computational analysis using quantum chemistry casts serious doubt on these suggestions: these pathways have enormous activation barriers and in constrast to what is observed experimentally, they overwhelmingly favor a racemic product. Instead we propose that a suprafacial [1,3]-prototopic shift occurs in a two-step deprotonation/reprotonation sequence. This mechanism is favored by 15 kcal mol<sup>-1</sup> over that previously proposed. Most importantly, this is also consistent with stereospecificity since reprotonation occurs rapidly on the same p-face. We have used explicitly-solvated molecular dynamics studies to study the persistence and condensed-phase dynamics of the intermediate ion-pair formed in this reaction. Chirality transfer is the result of a particularly resilient contact ion-pair, held together by electrostatic attraction and a critical NH···p interaction which ensures that this species has an appreciable lifetime even in polar solvents such as DMSO and MeOH.

scholarly journals Tripodal, Squaramide-Based Ion Pair Receptor for Effective Extraction of Sulfate Salt

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2751
Author(s):  
Damian Jagleniec ◽  
Marcin Wilczek ◽  
Jan Romański
Keyword(s):  
Ion Pairs ◽  
Binding Mode ◽  
Selective Extraction ◽  
Ion Pair ◽  
Hofmeister Series ◽  
Sulfate Salt ◽  
Lower Affinity ◽  
High Affinity ◽  
Binding Domains ◽  
Hydrated Sulfate

Combining three features—the high affinity of squaramides toward anions, cooperation in ion pair binding and preorganization of the binding domains in the tripodal platform—led to the effective receptor 2. The lack of at least one of these key elements in the structures of reference receptors 3 and 4 caused a lower affinity towards ion pairs. Receptor 2 was found to form an intramolecular network in wet chloroform, which changed into inorganic–organic associates after contact with ions and allowed salts to be extracted from an aqueous to an organic phase. The disparity in the binding mode of 2 with sulfates and with other monovalent anions led to the selective extraction of extremely hydrated sulfate anions in the presence of more lipophilic salts, thus overcoming the Hofmeister series.

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