Mechanisms of Photoreactions in Solutions. I. Reduction of Benzophenone by Benzhydrol

Moore, William M.; Hammond, George S.; Foss, Robert P.

doi:10.1021/ja01474a001

Cited by 238 publications

(95 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…[7] For the positive photoreaction mechanism of PDMS, benzophenone is introduced and mixed with PDMS monomers to generate free radicals under near-UV radiation ($365 nm). [7,[28][29][30] These radicals react with the silicon hydride groups in the PDMS crosslinkers first and prevent them from undergoing the traditional crosslinking reactions with the PDMS monomer. During the post-exposure bake, the unexposed PDMS is fully crosslinked and cured, while the exposed PDMS remains uncrosslinked and can be washed away in toluene.…”

Section: Photoreaction Mechanismmentioning

confidence: 99%

Photopatternable Conductive PDMS Materials for Microfabrication

Cong

Pan

2008

Adv Funct Materials

174

122

View full text Add to dashboard Cite

Conductive photodefinable polydimethylsiloxane (PDMS) composites that provide both high electrical conductivity and photopatternability have been developed. The photosensitive composite materials, which consist of a photosensitive component, a conductive filler, and a PDMS pre‐polymer, can be used as a negative photoresist or a positive photoresist with an additional curing agent. A standard photolithographic approach has been used to fabricate conductive elastomeric microstructures. Feature sizes of 60 µm in the positive photoresist and 10 µm in the negative photoresist have been successfully achieved. Moreover, as the conductive filler, silver powders significantly improve the electrical conductivity of the PDMS polymer, but also provide enhanced mechanical and thermal properties as well as interesting biological properties. The combined electrical, mechanical, thermal, and biological properties along with photopatternability make the PDMS‐Ag composite an excellent processable and structural material for various microfabrication applications.

show abstract

Section: Photoreaction Mechanismmentioning

confidence: 99%

Photopatternable Conductive PDMS Materials for Microfabrication

Cong

Pan

2008

Adv Funct Materials

174

122

View full text Add to dashboard Cite

show abstract

“…3 The molecular photophysics and photochemistry of benzophenone and its derivatives in fluid organic solvents represent a keystone in the development and history of mechanistic organic photochemistry. 4 Photoexcitation of BP to the S 1 state is followed by rapid intersystem crossing (ISC) with unit quantum yield to the triplet state.…”

Section: Introductionmentioning

confidence: 99%

The S₂ → S₁ Internal Conversion of Benzophenone and p-Iodobenzophenone

2004

View full text Add to dashboard Cite

Two modes of excitation (S 0 f S 2 and S 0 f S 1 ) of benzophenone (BP) and p-iodobenzophenone (p-IBP) in acetonitrile have been examined by ultrafast pump-probe experiments. The S 1 states (λ max ∼ 575-580 nm) of BP and p-IBP were observed to be generated with lifetimes of 0.53 and 0.59 ps, respectively, following excitation at 267 nm, and this has been attributed to the S 2 f S 1 internal conversion. The rates of the S 1 f T 1 ISC have been observed to be similar following either 267 or 335 nm excitation for both BP (∼1 × 10 11 s -1 ) and p-IBP (∼2.3 × 10 11 s -1 ).

show abstract

“…(11)(12)(13)(14) in which only C-H bonds (and not the -OH group) have been found to react with the carbonyl compounds. It appears 'likely that the tautomerism involving the symmetrical adduct structures [A] contributes at least partially to the lowering of the energy of the postulated charge-transfer state, such that the primary photochemical reaction can be triggered by a red-to-blue photon upconversion process (4).…”

mentioning

confidence: 99%

“…If, in the charge-transfer state, the ring V j3-ketoester group exists in the enol form, we readily observe that quantum numbers s = 0 and m, = 0 are explicitly given. Likewise, we denote the three degenerate components of the pure triplet Ti by 13,111), 13 …”

mentioning

confidence: 99%

“…The-avefunctions in this case are given by the symmetric state 3*1(A) = >g (|3t(1))| 1o(2)) + |IlIo(l))I8d1(2))) [12] and the antisymmetric state = ....L (| si(1))I4 o(2)) -|j4 o(())8d1,i(2))) [13] Since dipole coupling between 114) and I4't) occurs only through the singlet admixture in '$i< (see Eq. 4), the energy of the splitting between 814t(A) and 1t41(B) is found to be 0.4 t(6/A)2, which is considerably smaller than that 2 t between-l*(A) and l{'(B).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Molecular Basis for the Photosynthetic Primary Process

Fong

1974

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

In this paper, the molecular details for the primary reaction in photosynthesis are deduced from several recent critical experimental observations. A symmetrical structure is proposed for the basic unit of the reaction center in plant photosynthesis. A mathematical consequence of the symmetrical arrangement is the creation of an anomalously long-lived trap state, which makes possible the summation of a reaction-center triplet excitation and an antenna chlorophyll singlet excitation to bring the photoactive chlorophylls to a charge-transfer state prior to entering into a primary photochemical reaction.It has long been recognized that certain chlorophyll (Chl)-a molecules in plants and photosynthetic bacteria are capable of performing highly efficient photochemical work under the illumination of relatively low-energy photons in the near infrared. No parallel situation exists in chemistry. Chlorophyll-a molecules by themselves are not photochemically activated by visible or infrared photons.In existing theories (1-3), the possible involvement of the excited singlet and triplet eigenstates of the Chl-a molecule in the primary photochemical reactions has been considered.In a recent paper (4), I suggested a basic mechanism for the primary reaction in photosynthesis. Through interactions between the lowest-lying triplet state of the reaction-center chlorophylls and the first excited singlet state of the antenna chlorophylls, absorbed light quanta are upconverted to a higher-lying charge-transfer state. In this paper, the molecular details of the energy-upconversion reaction are described in terms of experimental observations and first principles. Nature of the photoactive charge-transfer stateIn seeking the most probable configuration for the reactioncenter chlorophylls, we take into cognizance: (i) the recent finding (5-10) that the primary photooxidation product of in vivo photosynthesis contains a special pair of Chl molecules over which the spin density is equivalently distributed and (ii) in vitro mixtures of Chl and H20 give rise to photoactive 1: 1 Chl-H20 adducts (10). We propose an interesting symmetrical (C2) structure (see Fig; 1) in which the two parallel porphyrin rings of the Chl molecules are complementarily held in position by two H20 molecules, each being involved in a hydrogen bond to the carbonyl of the ring V carbomethoxy group of one Chl molecule and an oxygen coordination bond to the magnesium atom of the second Chl molecule. This structure is a modification of the original Katz model (10) in which the two chlorophyll molecules are asymmetrically Abbreviation: Chl, chlorophyll. linked by a single H20 molecule with one chlorophyll acting as an electron donor and the second an acceptor. The symmetry of the present model, which appears to be consistent with the observation of the equivalent spin distribution in the photooxidized special pair, suggests a number of theoretical possibilities. Upon light excitation, for example, two equivalent tautomeric forms of the postulated charge-transfer...

show abstract

Mechanisms of Photoreactions in Solutions. I. Reduction of Benzophenone by Benzhydrol

Cited by 238 publications

References 0 publications

Photopatternable Conductive PDMS Materials for Microfabrication

Photopatternable Conductive PDMS Materials for Microfabrication

The S₂ → S₁ Internal Conversion of Benzophenone and p-Iodobenzophenone

Molecular Basis for the Photosynthetic Primary Process

Contact Info

Product

Resources

About

Mechanisms of Photoreactions in Solutions. I. Reduction of Benzophenone by Benzhydrol

Cited by 238 publications

References 0 publications

Photopatternable Conductive PDMS Materials for Microfabrication

Photopatternable Conductive PDMS Materials for Microfabrication

The S2 → S1 Internal Conversion of Benzophenone and p-Iodobenzophenone

Molecular Basis for the Photosynthetic Primary Process

Contact Info

Product

Resources

About

The S₂ → S₁ Internal Conversion of Benzophenone and p-Iodobenzophenone