Reversible Photoinduced Ligand Substitution in a Luminescent Chromium(0) Complex

Light-triggered dissociation of ligands forms the basis for many compounds of interest for photoactivated chemotherapy (PACT), in which medicinally active substances are released or "uncaged" from metal complexes upon illumination. Photoinduced ligand dissociation is usually irreversible, and many recent studies performed in the context of PACT focused on ruthenium(II) polypyridines and related heavy metal complexes. Herein, we report a first-row transition metal complex, in which photoinduced dissociation and spontaneous recoordination of a ligand unit occurs. Two scorpionate-type tridentate chelates provide an overall six-coordinate arylisocyanide environment for chromium(0). Photoexcitation causes decoordination of one of these six ligating units and coordination of a solvent molecule, at least in tetrahydrofuran and 1,4-dioxane solvents, but far less in toluene, and below detection limit in cyclohexane. Transient UV-vis absorption spectroscopy and quantum chemical simulations point to photoinduced ligand dissociation directly from an excited metal-to-ligand charge-transfer state. Owing to the tridentate chelate design and the substitution lability of the first-row transition metal, recoordination of the photodissociated arylisocyanide ligand unit can occur spontaneously on a millisecond time scale. This work provides insight into possible self-healing mechanisms counteracting unwanted photodegradation processes and seems furthermore relevant in the contexts of photoswitching and (photo)chemical information storage.

Iron(III) Carbene Complexes with Tunable Excited State Energies for Photoredox and Upconversion

Substituting precious elements in luminophores and photocatalysts by abundant first-row transition metals remains a significant challenge, and iron continues to be particularly attractive owing to its high natural abundance and low cost. Most iron complexes known to date face severe limitations due to undesirably efficient deactivation of luminescent and photoredox-active excited states. Two new iron(III) complexes with structurally simple chelate ligands enable straightforward tuning of ground and excited state properties, contrasting recent examples, in which chemical modification had a minor impact. Crude samples feature two luminescence bands strongly reminiscent of a recent iron(III) complex, in which this observation was attributed to dual luminescence, but in our case, there is clear-cut evidence that the higher-energy luminescence stems from an impurity and only the red photoluminescence from a doublet ligand-to-metal charge transfer (2LMCT) excited state is genuine. Photoinduced oxidative and reductive electron transfer reactions with methyl viologen and 10-methylphenothiazine occur with nearly diffusion-limited kinetics. Photocatalytic reactions not previously reported for this compound class, in particular the C-H arylation of diazonium salts and the aerobic hydroxylation of boronic acids, were achieved with low-energy red light excitation. Doublet-triplet energy transfer (DTET) from the luminescent 2LMCT state to an anthracene annihilator permits the proof of principle for triplet-triplet annihilation upconversion based on a molecular iron photosensitizer. These findings are relevant for the development of iron complexes featuring photophysical and photochemical properties competitive with noble-metal-based compounds.

Luminescence and Excited-State Reactivity in a Heteroleptic Tricyanido Fe(III) Complex

Harnessing sunlight via photosensitizing molecules is key for novel optical applications and solar-to-chemical energy conversion. Exploiting abundant metals such as iron is attractive but becomes challenging due to typically fast nonradiative relaxation processes. In this work, we report on the luminescence and excited-state reactivity of the heteroleptic [FeIII(pzTp)(CN)3]- complex (pzTp = tetrakis(pyrazolyl)borate), which incorporates a σ-donating trispyrazolyl chelate ligand and three monodentate σ-donating and π-accepting cyanide ligands. Contrary to the nonemissive [Fe(CN)6]3-, a broad emission band centered at 600 nm at room temperature has been recorded for the heteroleptic analogue attributed to the radiative deactivation from a 2LMCT excited state with a luminescence quantum yield of 0.02% and a lifetime of 80 ps in chloroform at room temperature. Bimolecular reactivity of the 2LMCT excited state was successfully applied to different alcohol photo-oxidation, identifying a cyanide-H bonding as a key reaction intermediate. Finally, this research demonstrated the exciting potential of [Fe(pzTp)(CN)3]- as a photo-oxidant, paving the way for further exploration and development of emissive Fe-based photosensitizers competent for photochemical transformations.

Visible-Light-Driven CO2 Reduction with Homobimetallic Complexes. Cooperativity between Metals and Activation of Different Pathways

Visible-light-driven reduction of CO2 to both CO and formate (HCOO-) was achieved in acetonitrile solutions using a homobimetallic Cu bisquaterpyridine complex. In the presence of a weak acid (water) as coreactant, the reaction rate was enhanced, and a total of ca. 766 TON (turnover number) was reached for the CO2 reduction, with 60% selectivity for formate and 28% selectivity for CO, using Ru(phen)32+ as a sensitizer and amines as sacrificial electron donors. Mechanistic studies revealed that with the help of cooperativity between two Cu centers, a bridging hydride is generated in the presence of a proton source (water) and further reacts with CO2 to give HCOO-. A second product, CO, was also produced in a parallel competitive pathway upon direct coordination of CO2 to the reduced complex. Mechanistic studies further allowed comparison of the observed reactivity to the monometallic Cu quaterpyridine complex, which only produced CO, and to the related homobimetallic Co bisquaterpyridine complex, that has been previously shown to generate formate following a mechanism not involving the formation of an intermediate hydride species.

A CuICoII cryptate for the visible light-driven reduction of CO2

Among the rare bimetallic complexes known for the reduction of CO2, CoIICoII and ZnIICoII hexamine cryptates are described as efficient photocatalysts. In close relation to the active sites of natural, CO2-reducing enzymes, we recently reported the asymmetric cryptand {NSNN}m ({NSNN}m = N[(CH2)2SCH2(m-C6H4)CH2NH(CH2)2]3N) comprising distinct sulphur- and nitrogen-rich binding sites and the corresponding CuIMII (MII = CoII, NiII, CuII) complexes. To gain insight into the effect of metals in different oxidation states and sulphur-incorporation on the photocatalytic activity, we herein investigate the CuICoII complex of {NSNN}m as catalyst for the visible light-driven reduction of CO2. After 24 h irradiation with LED light of 450 nm, CuICoII-{NSNN}m shows a high efficiency for the photocatalytic CO2-to-CO conversion with 9.22 μmol corresponding to a turnover number of 2305 and a high selectivity of 98% over the competing H2 production despite working in an acetonitrile/water (4 : 1) mixture. Experiments with mononuclear counterparts and computational studies show that the high activity can be attributed to synergistic catalysis between Cu and Co. Furthermore, it was shown that an increase of the metal distance results in the loss of synergistic effects and rather single-sited Co catalysis is observed.

A machine-learning tool to predict substrate-adaptive conditions for Pd-catalyzed C-N couplings

Machine-learning methods have great potential to accelerate the identification of reaction conditions for chemical transformations. A tool that gives substrate-adaptive conditions for palladium (Pd)-catalyzed carbon-nitrogen (C-N) couplings is presented. The design and construction of this tool required the generation of an experimental dataset that explores a diverse network of reactant pairings across a set of reaction conditions. A large scope of C-N couplings was actively learned by neural network models by using a systematic process to design experiments. The models showed good performance in experimental validation: Ten products were isolated in more than 85% yield from a range of couplings with out-of-sample reactants designed to challenge the models. Importantly, the developed workflow continually improves the prediction capability of the tool as the corpus of data grows.

Organophotocatalytic Aerobic Oxygenation of Phenols in a Visible-Light Continuous-Flow Photoreactor

A mild photocatalytic phenol oxygenation enabled by a continuous-flow photoreactor using visible light and pressurized air is described herein. Products for wide-ranging applications, including the synthesis of vitamins, were obtained in high yields by precisely controlling principal process parameters. The reactor design permits low organophotocatalyst loadings to generate singlet oxygen. It is anticipated that the efficient aerobic phenol oxygenation to benzoquinones and p-quinols contributes to sustainable synthesis.

The radiological diagnosis of cerebral venous angioma: cerebral angiography and computed tomography

The angiographic and CT findings in seven cases of cerebral venous angioma are presented and analyzed. Two cases were also examined with dynamic CT. The radiological literature on the subject is reviewed and a new classification of cerebral venous angioma based on its pattern of drainage is proposed. It is concluded that with the use of thin slices and coronal cuts both the angioma and its pattern of venous drainage can be identified on CT in a high proportion of cases. In addition, with dynamic CT the specificity of CT in diagnosing cerebral venous angioma may further increase.

[Ultrasound-controlled fine needle puncture of gastrointestinal tumors with continuous view]

On account of its principle, ultrasound tomography cannot be recommended as a screening method for intestinal tumors; nevertheless, it may sometimes demonstrate larger tumors not producing typical signs. These neoplasms show a characteristic pattern ("cockade phenomenon"). In the region of the antrum they appear occasionally as a rigid thickening of the gastric wall. The nature of such an expansive lesion may be evaluated quickly and safely by a fine-needle puncture performed under sonographic control. No complications have been observed so far.

The current state of the radiological diagnosis of acoustic neuroma

Thin, overlapping section, contrast-enhanced, axial and coronal CT, with additional high-resolution (HR) treatment of the sections through the internal auditory canal, was performed on 31 patients clinically suspected of acoustic neuroma. With this technique 13 acoustic neuromas protruding more than 10 mm and eight acoustic neuromas protruding between 2 and 10 mm outside the internal auditory canal were unequivocally diagnosed. O2CT cisternography was performed on ten patients. An intracanalicular neuroma was diagnosed in three cases with this technique, also a small extracanalicular neuroma in one case, and an acoustic neuroma was definitely excluded in six cases. It is concluded that O2CT cisternograhy is the diagnostic procedure of choice for the detection of purely intracanalicular neuromas and the definite exclusion of acoustic neuroma. HR CT proved superior to polytomography for the evaluation of the internal auditory canal and should be performed in every case suspected of acoustic neuroma. A protocol for the radiological investigation of patients suspected of acoustic neuroma is given.

Intramural pseudodiverticulosis of the esophagus: report of seven cases and literature review

Seven cases of esophageal intramural pseudodiverticulosis (EIPD) are presented and compared with 46 cases previously reported. EIPD is mainly a disease of older age with a 3:2 predominance of male patients. The radiologic appearance of EIPD shows great variation in localization and severity of visible changes. Radiologic examination is far more sensitive than endoscopy in diagnosing EIPD. The most effective therapy for EIPD is dilatation of strictures, leading to amelioration or disappearance of symptoms in over 90% of cases. Visible pseudodiverticula may persist after therapy, even in symptom-free patients.

[Experience with sonographically controlled fine-needle punctures with permanent visual control (author's transl)]

With our new biopsy-device it is now possible to perform fine-needle punctures of lesions in the abdomen, thoracic cage, cervical region and extremities under continuous visual control. This intervention can easily be done with low risk for the patient and can be repeated whenever necessary. It has proven its advantages for amniocentesis as well, especially in cases with a low amount of amniotic fluid. Moreover, our new device allows the combination of sonographical and radiological interventions, for example of the kidneys.

[Correlation the laevocardiogram and plain chest films in the presence of myocardial insufficiency (author's transl)]

A correlation was attempted in 106 patients with myocardial insufficiency between linear and volume parameters of the laevocardiogram and the corresponding parameters on plain chest films, as well as between pressure measurements and the degree of pulmonary congestion. Measurements on the plain radiograph provide only limited information on the function of the myocardium and the severity of myocardial lesion respectively. Nevertheless, they are of some value during the course of the disease.

Computed tomography of acoustic neuromas with emphasis on small tumor detectability

The results of CT analysis of 41 acoustic neuromas are presented. Large and medium-sized tumors are easily detected: our results are comparable to the reported findings of other authors. The detectability of small acoustic neuromas is considerably improved by the application of newer-generation CT apparatus and the use of specific scanning parameters, including extremely thin overlapping slices, low scan speed, high gantry tilt, short time between contrast agent application and tumor scanning, and computer-assisted magnification of the posterior fossa.

[Abeurysm of the septum membranaceum]

Between 1968 and 1977 5000 angiocardiographies revealed an aneurysm of the membranous septum (AMS) in 20 patients. In 11 patients the AMS was accompanied by a usually minor ventricular septal defect, in 4 by aortic valve disease, in 3 by coronary heart disease and in the remainder by some other rare heart disease. The diagnosis of AMS was established by angiocardiography, but in 3 patients it was detected by echocardiography. In one case a sepsis lenta with cerebral embolization was observed.

[Possibilities and limits of xeroradiography. A statement (author's transl)]

Xeroradiography has proved to be of particular use for the examination of soft tissues. Due to great latitude and edge enhancement effect alterations of the splanchnocranium, the breast and the juxtaosseous soft tissues are especially well recognizable. Also for examination of larynx and trachea as well as certain soft tissues in the region of the neck this method is advantageous and proves its facilities to demonstrate diseases of the lungs and hilar region. On the contrary, alterations of the vertebral column, the basis of the skull and the abdomen cannot be examined by means of xeroradiography because of not justified radiation dosage. Xeroradiography offers no advantage for arthrography, angiography and examination of bones and skeletal parts of joints.

[Radiological diagnosis of the narrow lumbar spinal canal syndrome (author's transl)]

31 myelograms of patients with the syndrome of lumbar spinal canal constriction were analysed. Two forms can be distinguished - a primary form with hypoplasia of the lumbar section of the spinal canal, and a secondary form with circumscribed constriction through olisthy or spondylosis deformans. The characteristics symptoms of the primary form (n = 21) are: difficult lumbar puncture, the ascent of the contrast medium in the thoracic section of the vertebral canal, multiple protrusions of the intervertebral discs, reduced sagittal diameter of the dural area which is marked by additional signs of spondylosis. In this connection, the alterations were so characteristic that it was possible to diagnose the condition even before the operation. The myelogram with water-soluble contrast-medium is considered to be markedly superior to other methods of radiological examination.

[Abdominal plain films in mesenterial infarct]

86 plain films of the abdomen from 63 patients with acute mesenteric infarction were compared with plain films of 90 patients with acute abdomen of different origin. The airless abdomen, the increased thickness of the gut wall and the hairpin sign proved tbe nonspecific, but more pronounced and more frequent in mesenteric infarction. Gas in the gut wall and in the portal vein system was found only in mesenteric infarction. All 6 patients with gas in the portal veins died. The airless abdomen in a patient with severe abdominal pain is a surprising finding and points to the possibility of mesenteric infarction.

[Side reaction after lumbar myelography with dimer-x (author's transl)]

The existence of several very impressive spinal paroxysms after lumbar myelography with Dimer-X1 caused us to make a retrospective investigation of 327 patients with 355 myelographies. In 7.1% of the investigations we have found partly heavy, but mostly reversible neurological complications. The latter cannot be classified, contrary to prevailing statements, in spinal, meningeal or cerebral reactions, since mostly all 3 anatomical structures are being concerned. Corresponding casuistical information are being presented and with their neurological symptomatic discussed. The spinal paroxysms appeared approximately 6 hours after the myelography and lasted over 8-10 hours, in spite of intensive therapeutical efforts. The pathogenesis points to a multifactorial occurrence caused by the coincidence of an increased dosage of the contrast media, too bed rest time, rising of the contrast media in the spinal cord zone and disturbed liquor fluid circulation and contrast media resorption. Pathophysiologically is in connection with spinal cramps an epileptic mechanism probable. Additional spinal reflexive components could be an explanation for the little therapeutical effect of Diacepam (Valium), which is contrary to the statement in the literature. We have seen a better effect in particular cases with Phenothiazine. With strict observance of specific precautionary measures, the Dimer-X seems to be a good media for the presentation of the lumbar subarachnoid space. A further development in this field is desirable.

[Large solitary aneurysm of the left coronary artery. Plain films and angiography (author's transl)]

The diagnosis of coronary aneurysms has for a long time been made at autopsy. After a general review of coronary artery aneurysms, a large aneurysm of the circumflex branch of the left coronary is described; this was diagnosed by selective coronary angiography and successfully treated by surgery. The results are compared with six other reported cases of pre-operatively diagnosed coronary artery aneurysms. Since complications, such as rupture, embolisation or infarction, are common in large coronary aneurysms, early diagnosis is desirable. An abnormal bulge of the cardiac contour or circular calcification within or at the edge of the cardiac shadow may be suggestive of the diagnosis.

Arteriographic findings in hyperergic granulomatosis and vasculitis of a kidney

A case with a probable diagnosis of a limited form of Wegener's granulomatosis is presented. Arteriography of an involved kidney revealed arterial occlusions and stenoses with infarcted parenchymal regions and a distinct collateral circulation. Compared to the renal changes in other collagenous diseases, the renovasographic findings in this case were more prominent, more centrally located, and of segmental distribution.

[Directions for mammography from a radiological viewpoint]

A significant decrease in mortality due to breast cancer is feasible only by earlier diagnosis. The decisive screening method is mammography, which permits identification of a malignancy in its earliest stages. Indirect and direct signs of malignancy exist whose detection necessitates biopsy. Radiological examination of the tissue sample permits evaluation of the adequacy of excision and thus renders possible specific histological examination of the region of interest. Pneumocystography is a method for simultaneous diagnosis and therapy of benign cysts.

Diffuse lymphangiomyomatosis

A case of diffuse lymphangiomyomatosis with involvement of the large veins of the body is reported. The clinical, pathologoanatomic and especially the roentgenologic findings are described. Interstitial lung thickening, pleural effusions and spontaneous pneumothorax are findings which together with a stasis in the lymphatic system strongly suggest the diagnosis. The extensive involvement of the venous system supports the theory of a hamartomatous nature of the disease.

[Cinegeometric analysis of left ventricular function in normals and in patients with isolated stenosis of the ramus anterior descendens (author's transl)]

The left ventricular function was evaluated by a cineangiographic method. 28 normals and 36 patients with an isolated stenosis of the anterior descending branch of the left coronary artery underwent this procedure. From single plane RAO-LV-cineangiograms following parameters were calculated: LV-volumens (EDV, ESV) according to the area-length method, ejection fraction (EF), percentage shortening of the medial perpendicular short axis (delta M, delta MPL), mean velocity of circumferential fiber shortening (VCF, VCFPL). Patients with comparable ramus anterior descendens branch findings can have normal- or abnormal pattern of LV-contraction. The critical cineangiographic parameters of left ventricular function are significantly decreased at rest in ramus anterior descendens lesions with normal systolic anterior wall motion in comparison to the normal collective. Hypokinesis, Akinesis and aneurysms deteriorate parameters of LV-function.

[A comparison of xero-tomography of the lung hilum with conventional tomography (author's transl)]

Because of its particular photoelectric properties, xero-tomography is particularly suited for the investigation of abnormalities in the hilar regions. It is superior to conventional tomography because of the improved edge contrast, which emphasises details of relatively non-opaque structures, and because of its high exposure latitude. This justifies its use despite the higher radiation dose that is necessary. The demonstration of relatively dense and of more transradient tissues on the same picture by xero-tomography, and the ability to read it by ordinary light, makes it less tiring to interpret than the translucencies of conventional radiographs.

Diagnostic value of meatocisternography

Based on a review of 123 consecutive examinations a classification of ten types of meatocisternograms is proposed. Surgical correlation in 53 of these cases has shown that other causes of intrameatal filling defects may mimic acoustic neurinoma presence. Furthermore, grouping of these 123 patients into three clinical groups on the basis of symptoms and findings has not resulted in a clear type correlation when using a mixture of the ethyl esters of 9- and 10- monoiodostearates (Duroliopaque). Based on an experience using this classification in well over 500 meatocisternograms, several proposals are made for the clinical management of cases of clear-cut or suspect acoustic neurinomas.

[Cineangiographic left ventricular dimensional analysis in normal subjects and patients with coronary disease]

The cineangiographically determined left ventricular function was studied in normals and in CAD-patients with one- and three-vessel disease. From single plane RAO-LV-cineangiograms following parameters were calculated; LV-volumes (EDV, ESV) according to the area-length method, ejection fraction (EF), percentage shortening of the medial perpendicular short axis delta (M,deltaMpl), mean velocity of circumferential fiber shortening (V(CF), V(CFPL)). It can be concluded that there is 1. no correlation between the severity of coronary heart disease and the morphological left ventricular wall lesions, 2. a depressed left ventricular function in coronary heart disease and normal ventriculograms, 3. a more impaired left ventricular function when cineangiograms show hypokinesis or aneurysms, 4. hypokinesis or aneurysms in the anterior wall leads to a more depressed left ventricular function than the same lesions in the posterior wall.

[The effect of aneurysm resection on left ventricular function]

The effect of successful aortocoronary artery bypass surgery on left ventricular (LV) function was studied by angiography in 13 patients with coronary-artery disease and resection of a ventricular aneurysm. The following were calculated from single-plane right anterior oblique LV cine-angiograms: LV end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), percentage shortening of the medial perpendicular short axis (deltaM), mean velocity shortening of the circumferential fibres (VCF). The changes in the five hemi-axes of the anterior LV wall, and five of the inferior wall were averaged to give a value for relative anterior wall motion (SMV) and inferior wall motion (SMH). Changes in apical motion (SMS) were calculated from the percentage changes in the base-to-apex axis. The following mean values (x plus or minus s) were obtained four months before and 11 months after aneurysmectomy: EDVI (ml/m2) 154 plus or minus 27 (126 plus or minus 23), ESVI (ml/m2) 107 plus or minus 28 (56 plus or minus 15), SVI (ML/M2) 46.5 plus or minus 12.7 (69.9 plus or minus 23.1), EF (%) 32.6 plus or minus 8.0 (54.6 plus or minus 12.0), SMV (%) 6.1 plus or minus 10.0 (25.0 plus or minus 13.4), SMH (%) 25.9 plus or minus 13.1 (31.2 plus or minus 11.1), SMS (%) 5.1 PLus or minus 3.4 (13.1 plus or minus 4.2). These results indicated significant improvement in ventricular pumping action and wall motion after aneurysm resection and aortacoronary bypass surgery in patients with coronary-artery disease and severe cardiac failure.