Photo-inactive

For the case of stilbenecarboxylate (SBC, Fig. 9.9b), by comparison, both syn head-to-head and syn head-to-tail cyclodimers were formed. The product selectivity may also be controlled by the presence of co-absorbed photo-inactive molecules e.g. phenylbenzoate (Fig. 9.9c).The nature of the photodimerisation products can to some extent be controlled by changing the M2+/M3+ ratio, and hence the packing density of the incorporated monomer [113]. Norrish type II reactions of aromatic ketocarboxylates within the interlayer of MgAl-LDHs have also been studied [114]. 

The reaction mechanism has been described in ref, (23), The reaction is carried out at temperatures <-10°C where no dark thermal activity of the metal can be detected. It only occurs when near-UV light is admitted onto the solid, thus showing that the active phase is constituted by the support. However, the presence of a metal (Pt,Ni) is required to confer a catalytic character to the reaction since, otherwise, the reaction carried out on the bare support declines and stops after a certain time corresponding to an exhaustion of non-renewable active sites. These sites have been identified as deuterated hydroxyl groups since naked titania either dehydroxylated or pretreated in instead of is totally photo-inactive,... 

Two types of copolymers of ACN were investigated in this work. The first type contains ACN units separated by photo-inactive groups in the main chain such as AN or MAN. This permits a comparison of the homopolymer, PACN, to polymers containing smaller numbers of chromophores and the latter being randomly spaced along the polymer chain. The second type is a copolymer of ACN and another monomer containing different chromophore. In the first type only excited singlet, A, and excimers, CAAl are important states while in the second type two excimers, CAA) and CBB), and the exciplex (AB) are possible. 

ACN had the longest migration length of 70A compared to 63 A for PACN using equation (1). The above percentages correspond to an overall monomer composition of 1 1 and 4 1. Random poly(ACN-co-AN) showed monomeric fluorescence at 355 nm and excimer fluorescence at 405 nm. The Iq/Im ratios were 0.88 and 0.61 for the 47 and 80 ACN copolymers, respectively, and the same value for PACN was 0.52. The incorporation of photo-inactive units such as AN in the copolymer increase chain flexibility and allows more excimer formation. 

To determine the conductivity type, note the direction of potential shift with illumination. If OCP moves Positive (towards more anodic potentials) with illumination, the material is p-type. If OCP moves Negative (towards more cathodic potentials), the material is n-type. If the potential did not change with illumination, there may be an issue with electrode fabrication/contacts, the material may be photo-inactive under these conditions, or the material may not be viable for PEC applications. If no response to illumination is observed, it is doubtfiil that the material, as mounted, wiU respond to any other photoelectrochemical characterization techniques. However, the researcher may still wish to perform CV scans as described in section Three-Electrode j-V and Photocurrent Onset to completely rule out photoactivity of the material. 

Vesicles of single chain a,co-dipolar diyne surfactants 54-56 are completdy photo-inactive except they are cosonicated with cholesterol The authors believe the photoinactivity to originate from the high surface curvature of the vesicles. Cholesterol, however, becomes incorporated in the outer half of the membrane, decreases the surface curvature and renders the vesicles photoreactive... 

The signal transduction in this system is thought to be derived from two separate, reversible complexations o-BBV /HPTS and o-BBV Vmonosac-charide. In the absence of sugar o-BBV and HPTS form a photo-inactive complex while in the presence of sugar o-BBV forms a boronate ester-complex. The boronate ester formation converts the dicationic viologen... 

In this section, we present a rigorous route based on QCL dynamics for deriving quantum lassical expressions for linear and third-order ORFs, which reflect nonequilibrium dynamics on multiple adiabatic surfaces as opposed to equilibrium ground state dynamics.As will be shown, these ORFs consist of contributions from several Liouville pathways that differ with respect to the surfaces on which the dynamics of the photo-inactive DOF takes place between light-matter interactions. 

We begin by assuming that the quantum mechanical system under study may be well-approximated by a mixed quantum lassical system driven by a classical radiation field, in which the photo-active DOF (i.e. chromophore) are treated quantum mechanically and the photo-inactive DOF (i.e. environment) are treated classically. The time-dependent Hamiltonian for this system is given by ... 

In order to simulate a chromophore s linear optical response as measured in one-dimensional IR (ID-IR) spectroscopy, we must consider its interaction with a single impulsive pulse at time t = 0 fs. Prior to the interaction with the pulse, the chromophore is assumed to be in its ground state and the photo-inactive DOF are in the corresponding thermal equilibrium state ... 

The QCL approach has also been used to rigorously derive mixed quantum-classical expressions for linear and third-order ORFs, which reflect the nonequilibrium dynamics of the photo-inactive DOF on multiple adiabatic surfaces... 

Sharma, R. et al.. Identification of photo-inactive phytochrome A in etiolated seedlings and photoactive phytochrome B in green leaves of the aurea mutant of tomato. Plant ]., 4, 1035,1993. 

MORSTADT L, GRABER P, DE PASCALIS L, KLEINIG H, SPETH V and BEYER P (2002) Chemiosmotic ATP synthesis in photo synthetically inactive chromoplasts from Narcissus pseudonarcissus L. linked to a redox pathway potentially also involved in carotene desaturation , Planta, 215, 132-40. 

Besides ruthenium porphyrins (vide supra), several other ruthenium complexes were used as catalysts for asymmetric epoxidation and showed unique features 114,115 though enantioselectivity is moderate, some reactions are stereospecific and treats-olefins are better substrates for the epoxidation than are m-olcfins (Scheme 20).115 Epoxidation of conjugated olefins with the Ru (salen) (37) as catalyst was also found to proceed stereospecifically, with high enantioselectivity under photo-irradiation, irrespective of the olefmic substitution pattern (Scheme 21).116-118 Complex (37) itself is coordinatively saturated and catalytically inactive, but photo-irradiation promotes the dissociation of the apical nitrosyl ligand and makes the complex catalytically active. The wide scope of this epoxidation has been attributed to the unique structure of (37). Its salen ligand adopts a deeply folded and distorted conformation that allows the approach of an olefin of any substitution pattern to the intermediary oxo-Ru species.118 2,6-Dichloropyridine IV-oxide (DCPO) and tetramethylpyrazine /V. V -dioxide68 (TMPO) are oxidants of choice for this epoxidation. 

In this case the quantity n indicates how many times the number of reactive particles adsorbed per unit surface increases under illumination (other external conditions remaining the same). Evidently, the rate of the heterogeneous reaction in which these particles participate will be a function of fi and thus will be sensitive to illumination. If An = Ap = 0 (photo-electrically inactive absorption of light), then according to (41) m = 1, and illumination has no effect on the reaction rate. 

The term photo induced catalytic reaction irrplies the photochemical generation of a catalyst C from a thermally stable and catalytically inactive precursor ML. Unlike the formation of the catalyst C, which is a photochemical reaction, the subsequent transformation of the substrate into the product B is an exclusively thermal process catalysed by C. If the catalyst is not consumed in the course of the reaction, the quantum yield, i.e. the nurrber of product molecules B formed per photons absorbed by M, may exceed unity. 

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