Photochromism, anomalous multi-banded fluorescence and laser properties of some amino- and tosyl-amino derivatives of oxadiazole

The multi-banded fluorescence and laser properties of 11 new amino- and tosylamino derivatives of 2,5-di(phenyl)-1,3,4-oxadiazole and oxadiazole in various solvents at 293 K are reported. All the compounds investigated possess intra-molecular hydrogen quasi-bond (IHB) of 4.6-5.2 kcal mol(-1) in the ground state. In the excited state they can undergo protolytic dissociation or intra-molecular photon-initiated transfer of proton and reveal anomalous fluorescence which cannot be explained within the framework of the Kasha and Kasha-Vavilov rules. Depending upon the excitation wavelength, solvent, concentration and pH of the medium, the compounds studied show a single, double, triple or even a four-banded fluorescence, which has not been reported earlier. The nature of multi-banded fluorescence is explained in terms of the possible photochromic processes in excited states. Quantum yields and decay times of the different fluorescence bands are reported. Anomalous dependence of quantum yield upon concentration of the solution is observed. Laser properties of the compounds studied are carefully tested. Laser action based on the fluorescence of the so-called bi-radical molecules is reported. Various possible arrangements of singlet and triplet levels of compounds investigated are discussed.

HSV1716 injection into the brain adjacent to tumour following surgical resection of high-grade glioma: safety data and long-term survival

Following standard treatment, the prognosis remains poor in patients with high-grade glioma and new therapies are urgently required. Herpes simplex virus 1716 (HSV1716) is an ICP34.5 null mutant that is selectively replication competent and shown to be safe and to replicate following injection into high-grade glioma. We demonstrate that following surgical resection, HSV1716 is safe when injected into the brain adjacent to excised tumour. In all, 12 patients with recurrent or newly diagnosed high-grade glioma underwent maximal resection of the tumour. HSV1716 was injected into eight to 10 sites around the resulting tumour cavity with the intent of infecting residual tumour cells. As clinically indicated, patients proceeded to further radiotherapy or chemotherapy. There has been no clinical evidence of toxicity associated with the administration of HSV1716. Longitudinal follow-up has allowed the assessment of overall survival compared to that of similar patients not treated with HSV1716. Three patients remain alive and clinically stable at 15, 18 and 22 months postsurgery and HSV1716 injection. Remarkably, the first patient in the trial, who had extensive recurrent disease preprocedure, is alive at 22 months since injection of HSV1716 and 29 months since first diagnosis. Imaging has demonstrated a reduction of residual tumour over the 22-month period despite no further medical intervention since the surgery and HSV1716 injection. In this study, we demonstrate that on the basis of clinical observations, there has been no toxicity following the administration of HSV1716 into the resection cavity rim in patients with high-grade glioma. The survival and imaging data, in addition to the lack of toxicity, give us confidence to proceed to a clinical trial to demonstrate efficacy of HSV1716 in glioma patients.

Fluorescence and laser properties of D2-, C2- and D3 symmetry series oligophenylenes

The fluorescence and laser properties of ten aromatic compounds, specially chosen from the p-oligophenylenes (D(2) symmetry) or m-oligophenylenes (C(2) or D(3) symmetry) are studied experimentally (at 293 K) and quantum chemically. The quantum yields, gamma and the decay times, tau(f) of fluorescence are measured for deaerated and non-deaerated cyclohexane solutions. The oscillator strengths, f(e) of the S(0)-->S(p) (1A-->(1)L(a)) and S(0)-->S(alpha) (1A-->(1)L(b)) transitions, fluorescence, k(f) and intersystem crossing, k(ST), rate constants, and natural lifetimes, tau(0)(T) are calculated. The lowest 1L(b), 1L(a) and 3L(b) (77 K) levels are determined. It is found that all p-oligophenylenes from p-terphenyl onwards are excellent, photochemically stable laser dyes although the solubility in this series decreases dramatically. On the basis of trends observed in p-oligophenylenes (D(2)-series) and on the properties of the experimentally studied m-oligophenylenes of the C(2)- and D(3)-series, the fluorescence and laser properties of other compounds from these series are estimated/predicted. It is shown, for the first time, that m-oligophenylenes of the C(2)-series, from 1,3-di(p-terphenyl)benzene will acquire fluorescence of 1L(a)-->(1)A nature and could be extremely effective laser dyes. It is also shown that m-oligophenylenes of the D(3)-series, from 1,3,5-tri(p-quaterphenyl)benzene will also acquire 1L(a)-->(1)A nature fluorescence and laser ability, although this would not be as good as that of compounds in the C(2)-series. It is concluded that m-oligophenylenes can be used not only for passive mode locking but some may also be used as laser dyes and scintillators. The results obtained are important for various practical purposes and theoretical considerations.

Influence of weak and strong donor groups on the fluorescence parameters and the intersystem crossing rate constant

The absorption and fluorescence properties of 35 specially selected methyl and stronger donor substituted benzene, naphthalene, biphenyl, anthracene and 2-azaanthracene compounds are studied experimentally (at 293 K) and quantum chemically. The fluorescence quantum yields, gamma, and decay times, tauf, for deaerated and non-deaerated solutions are measured. The oscillator strength, fe, natural lifetime, tauf 0 and fluorescence and intersystem crossing rate constants, kf and kST, are calculated for each compound. The orbital nature of the lowest excited singlet state, S1, is determined. The investigation shows that the introduction of methyl groups onto aromatic compounds may produce different effects. The symmetry and hence kST and kf may change. As a result, gamma will also change. Steric hindrance, possibly due to the CH3 group, will decrease kf while increasing kST. In cases where the introduction of the methyl group leaves the symmetry unchanged, there is a slight increase in kST and a slight decrease in kf. This effect is cumulative (more CH3 groups lead to a greater decrease in gamma) and can be explained by the torsional vibrations of the methyl groups. The introduction of strong donor groups usually produces dramatic changes. kST always increases, as does kf and the increase in kf is usually greater. Hence, gamma usually increases, sometimes dramatically. The nature of the S1 state changes from pipi* (for an aromatic molecule) to pil,pi*. There are three reasons for the observed increase in kST: (i) a decrease in symmetry; (ii) the internal heavy atom effect; and (iii) an improved mixing of the S(1pil,pi*) state with Ti states. It is also found that, in many cases, the effect of methyl and stronger donor groups on the fluorescence parameters and kST depends on the position of substitution, as well as changes in the molecular symmetry. The substituent groups have different effects on the p- and alpha-bands. The fluorescence parameters obtained and trends observed may be useful for different theoretical and practical purposes.

The potential for efficacy of the modified (ICP 34.5(-)) herpes simplex virus HSV1716 following intratumoural injection into human malignant glioma: a proof of principle study

We have previously demonstrated the safety of intratumoural administration of the selectively replication-competent herpes simplex virus mutant HSV1716 in patients with high-grade glioma (HGG). Here we show its potential for efficacy by demonstrating that the virus survives and replicates when injected into the tumours of patients. Since HSV replication is a cytolytic process it must result in tumour cell killing. Twelve patients with biopsy-verified HGG received an intratumoural injection of 10(5) plaque-forming units (p.f.u.) of HSV1716. Four to 9 days after inoculation, tumours were removed and assayed for evidence of viral replication. In two patients, HSV1716, in excess of the input dose was recovered from the injection site. HSV DNA was detected by PCR at the sites of inoculation in 10 patients and at distal tumour sites in four. HSV-specific antigen was detected in tumour tissue from two patients. In five patients an immunological response to HSV1716, as detected by changes in levels of IgG and IgM, was demonstrated. This study demonstrates that HSV1716 replicates in HGG without causing toxicity in both HSV-seropositive and -seronegative patients.

Luminescence-laser classification of heteroaromatic and aromatic compounds

The luminescent and laser properties of heteroaromatic and aromatic compounds are reviewed and discussed on the basis of all possible mutual arrangements of singlet and triplet states. All heteroaromatic compounds are divided into five classes. It is shown that a heteroaromatic compound can only be an effective laser dye if it belongs to class V (a situation where the Tnpi* level lies at higher energy than the S1(pipi*) level). Moreover, it is shown that the energy interval between the Tnpi* and S1(pipi*) states must be no less than 1000 cm - since the rate constant of the non-radiative process S1(pipi*)[symbol in text]Tnpi*[symbol in text]T1(pipi*) is usually 100 times greater than the fluorescence rate constant. The classification is extended to compounds with orbitals of pi/,pi*, pi,nupi* and pi/,nupi* nature. Pure aromatic compounds, the spectral-luminescent properties of which are solely determined by transitions of pi-electrons (pi --> pi*), are also divided into five classes, depending on the mutual arrangement of the Sp(1La), Salpha(1Lb), Tp(3La) and Tbeta(3Bb) states. It is found that only aromatic compounds of classes IV and V can be effective scintillators and laser dyes. It is also shown that the energy interval Salpha-Sp (for class IV) and Tbeta-Sp (for class V) must be no less than 1000 cm(-1). To illustrate the classifications for heteroaromatic and aromatic compounds, 12 specifically chosen compounds were studied experimentally and quantum chemically. The quantum yields, gamma and decay times, tauf of fluorescence in aerated and non-deaerated ethanol or cyclohexane solutions were measured. The oscillator strength, f(e), fluorescence rate constant, k(f), natural lifetimes, tauT(0) and intersystem crossing rate constants, kST are calculated. The laser ability of each of the compounds studied is tested. The suggested classification schemes can be extremely useful in the quest for effective scintillators and laser dyes among hypothetical heteroaromatic and aromatic molecules, enabling evaluation of these properties for a particular compound using only quantum chemical simulations.

Evolution of absorption, fluorescence, laser and chemical properties in the series of compounds perylene, benzo(ghi)perylene and coronene

Absorption. fluorescence and laser properties of perylene, benzo(ghi)perylene and coronene are studied experimentally (under the same conditions) and quantum chemically at room (293 K) and at low (77 and 4 K) temperatures and direct comparison is made between the results for each molecule. All the main absorption and fluorescence parameters such as oscillator strength, fe, quantum yield, gamma, decay time, tauf, fluorescence rate constant, kf (Einstein coefficient, A) and intersystem crossing rate constant, kST, are measured or calculated. The systems of singlet and triplet levels for these compounds are simulated and analyzed. Triplet states mixing with the lowest singlet S1 state are determined. The low values of kST found are explained. The possible vibronic coupling in the molecule coronene is discussed. The nature of the three fluorescence bands of coronene observed is interpreted. The change in the arrangement of the singlet and triplet levels of the studied compounds is interpreted quantum-chemically. It is found that at room temperature (293 K), only perylene shows laser action, while all three compounds show good laser oscillation at low temperature (< 100 K). The differences in the laser properties of these compounds are explained by the inversion of the Sp(1La) and Sinfinity(1Lb) levels which occurs in the transition from perylene to benzo(ghi)perylene. Chemical properties of the compounds studied are outlined. Linear and quasi-linear fluorescence spectra of perylene and benzo(ghi)perylene, obtained at 77 and 4 K. can be used in the identification of these compounds.

The influence of molecular symmetry and topological factors on the internal heavy atom effect in aromatic and heteroaromatic compounds

The absorption and fluorescence properties of 26 specially selected aromatic and heteroaromatic compounds, from different classes, are studied quantum chemically and experimentally at room temperature (293 K). Seven of these compounds have not been studied before. The compounds are arranged in seven groups, which illustrate different cases of the internal heavy atom effect. The quantum yield of fluorescence, gamma and fluorescence decay time, tau(f) of deaerated and non-deaerated cyclohexane or ethanol solutions are measured. The oscillator strength, f(e), fluorescence rate constant, k(f), natural lifetime, tau(0)t, and intersystem crossing rate constant, kST, were calculated for each compound. The orbital nature of the lowest excited singlet state and direction of polarization of the S0 --> S1 transitions are determined using the PPP-Cl method for each molecule. The investigation shows that substitution of a heavy atom(s) (Cl, S, Br, I etc.) into an aromatic or heteroaromatic molecule may produce different changes in all the fluorescence parameters (sometimes dramatically) and not necessarily lead to the quenching of fluorescence. Substitution of a heavy atom(s) may increase the value of the spin-orbit operator, Hso, if the S0 --> S1 excitation is localized to some extent on a carbon atom bonded to a heavy atom(s) or on the heavy atom itself (O or S). Such substitution may change the symmetry of a molecule and hence the values of the [psiS1/Hso/psi'T1] matrix elements would change (in molecules of higher symmetry groups not all Ti states are able to mix with the perturbing S1 state). Such substitution may change the arrangement of Ti states below the S1, state and hence, the Franck-Condon factors would change. Such substitution may also change the value of the [psiS0/Mj/psiS1] matrix element and, consequently, the oscillator strength of the S0 --> S1 transition would change. A combination of all these possible changes determines the value of k(f) and kST and, consequently, determines the value of gamma and tau(f). It is observed that in many cases, the value of the spin-orbit operator is related to the dipole moment operator, e.g. if the introduction of a heavy atom increases kST then, as a rule, it decreases f(e)(1A --> 1La).

The dependence of the fluorescence properties, laser properties and photochemical stability of aromatic compounds on the molecular symmetry

It is known that the spectral properties of organic compounds are, to a large extent, determined by the molecular symmetry. Numerous articles and monographs have been devoted to this problem. However, the influence of the molecular symmetry on fluorescence and, hence, laser parameters has not been fully investigated. In this paper, the fluorescence and laser properties of 20 aromatic compounds are experimentally studied at room temperature. The compounds studied are arranged in family-related pi-structure pairs. In each pair, even-numbered compounds belong to a higher symmetry group than odd-numbered compounds due to symmetrical substitution. All main fluorescence parameters such as quantum yield, gamma, decay time, tauf, fluorescence rate constant, k(f) (Einstein coefficient, A), and intersystem crossing rate constant, kST, are measured or calculated. It has been found that for most of the symmetrically substituted molecules, the value of kST decreases, sometimes very significantly. For example, the transition from 9-phenylanthracene (C2 symmetry) to 9,10-diphenylanthracene (D2 symmetry) is accompanied by an 18-fold decrease in the value of kST. This phenomenon is explained by the fact that, in a molecule of higher symmetry, not all triplet states mix with the fluorescing S1 state. It is also found that the symmetry of a molecule greatly affects laser parameters such as the threshold of laser action and the photochemical stability of a laser solution. It is observed that the threshold for even-numbered compounds is much lower and the photochemical stability, in most cases, is much higher than for odd-numbered compounds. These phenomena are discussed and explained.

Toxicity evaluation of replication-competent herpes simplex virus (ICP 34.5 null mutant 1716) in patients with recurrent malignant glioma

The herpes simplex virus (HSV) ICP34.5 null mutant 1716 replicates selectively in actively dividing cells and has been proposed as a potential treatment for cancer, particularly brain tumours. We present a clinical study to evaluate the safety of 1716 in patients with relapsed malignant glioma. Following intratumoural inoculation of doses up to 10(5) p.f.u., there was no induction of encephalitis, no adverse clinical symptoms, and no reactivation of latent HSV. Of nine patients treated, four are currently alive and well 14-24 months after 1716 administration. This study demonstrates the feasibility of using replication-competent HSV in human therapy.

Construction and characterization of herpes simplex virus type 1 mutants with conditional defects in immediate early gene expression

The herpes simplex virus type 1 (HSV-1) mutant in 1814 contains an insertion mutation in the coding sequence for the virion transactivator protein VP16 and is thus impaired for the activation of immediate early (IE) gene expression. This virus was modified further by introducing the Moloney murine leukemia virus LTR promoter in place of the upstream sequences controlling expression of the IE regulatory protein ICPO, to yield mutant in 1820. In almost all cell types tested, in 1820 initiated infection less efficiently than in 1814, behaving as if lacking both VP16 and ICPO functions, but in BHK cells in 1820 was less impaired than in 1814. A rescuant of in 1820 at the VP16 locus, in 1825, also exhibited a host range phenotype, initiating replication as efficiently as wild-type HSV-1 in BHK cells but inefficiently in other cell types. In 1825 was unable to complement an ICPO null mutant in restricted cells, demonstrating that the promoter exchange prevented the expression of ICPO protein in functionally significant amounts. The novel host range properties of in 1820 provided a basis for the construction of additional viruses conditionally impaired for IE gene expression and assessment of their value as prototype vectors. Production of an HSV-1 mutant multiply defective in the expression of IE gene products was achieved by introduction of the temperature-sensitive mutation of HSV-1 tsK, which inactivates the IE transcription activator ICP4 at nonpermissive temperatures, into in 1820 to produce in 1820K. This mutant could be propagated effectively in BHK cells at 31 degrees but was effectively devoid of the major regulators ICPO, ICP4, and VP16 in other cells types at 38.5 degrees. Cultures could withstand infection with 5 PFU of in 1820K per cell without detectable cytopathology and could be reseeded to form colonies at approximately 90% efficiency. A derivative of in 1820K containing the Escherichia coli lacZ gene controlled by the human cytomegalovirus (HCMV) major IE promoter expressed low but detectable levels of beta-galactosidase in almost all cells after infection of cultures at 5 PFU per cell and incubation at 38.5 degrees. Cultures infected with 5 PFU per cell of an in 1820K derivative expressing neomycin phosphotransferase (npt) controlled by the HCMV IE promoter were resistant to killing by the antibiotic G418 for up to 3 days, and cell survival correlated with the retention of functional levels of npt. Mutants based on in 1820K can thus express foreign gene products in virtually all cells in a culture under conditions in which cytotoxicity is eliminated, demonstrating that progressive reduction of IE gene expression is an important step in the design of HSV-1-derived vectors.