Mural Wnt/ß-catenin signaling regulates Lama2 expression to promote neurovascular unit maturation.

Neurovascular unit and barrier maturation rely on vascular basement membrane (vBM) composition. Laminins, a major vBM component, are crucial for these processes, yet the signaling pathway(s) that regulate their expression remain unknown. Here, we show that mural cells have active Wnt/ß-catenin signaling during central nervous system development in mice. Bulk RNA sequencing and validation using postnatal day 10 and 14 wild-type versus adenomatosis polyposis coli downregulated 1 (Apcdd1-/-) mouse retinas revealed that Lama2 mRNA and protein levels are increased in mutant vasculature with higher Wnt/ß-catenin signaling. Mural cells are the main source of Lama2, and Wnt/ß-catenin activation induces Lama2 expression in mural cells in vitro. Markers of mature astrocytes, including aquaporin 4 (a water channel in astrocyte endfeet) and integrin-α6 (a laminin receptor), are upregulated in Apcdd1-/- retinas with higher Lama2 vBM deposition. Thus, the Wnt/ß-catenin pathway regulates Lama2 expression in mural cells to promote neurovascular unit and barrier maturation.

Iron Dioxygen Adduct Formed during Electrochemical Oxygen Reduction by Iron Porphyrins Shows Catalytic Heme Dioxygenase Reactivity.

Heme dioxygenases oxidize the indole ring of tryptophan to kynurenine which is the first step in the biosynthesis of several important biomolecules like NAD, xanthurenic acid, and picolinic acid. A ferrous heme dioxygen adduct (or FeIII-O2•-) is the oxidant, and both the atoms of O2 are inserted in the product and its catalytic function has been difficult to emulate as it is complicated by competing rapid reactions like auto-oxidation and/or formation of the µ-oxo dimer. In situ resonance Raman spectroscopy technique, SERRS-RDE, is used to probe the species accumulated during electrochemical ORR catalyzed by site-isolated imidazole-bound iron porphyrin installed on a self-assembled monolayer covered electrode. These in situ SERRS-RDE data using labeled O2 show that indeed a FeIII-O2•- species accumulate on the electrode during ORR between -0.05 and -0.30 V versus Ag/AgCl (satd. KCl) and is reduced by proton coupled electron transfer to a FeIII-OOH species which, on the other hand, builds up on the electrode between -0.20 and -0.40 V versus Ag/AgCl (satd. KCl). This FeIII-OOH species then gives way to a FeIV═O species, which accumulates at -0.50 V versus Ag/AgCl (satd. KCl). When 2,3-dimethylindole is present in the solution and the applied potential is held in the range where FeIII-O2•- species accumulate, it gets oxidized to N-(2-acetylphenyl)acetamide retaining both the oxygens from O2 mimicking the reaction of heme dioxygenases. Turnover numbers more than 104 are recorded, establishing this imidazole-bound ferrous porphyrin as a functional model of heme dioxygenases.

Neuronal and glial regulation of CNS angiogenesis and barriergenesis.

Neurovascular pathologies of the central nervous system (CNS), which are associated with barrier dysfunction, are leading causes of death and disability. The roles that neuronal and glial progenitors and mature cells play in CNS angiogenesis and neurovascular barrier maturation have been elucidated in recent years. Yet how neuronal activity influences these processes remains largely unexplored. Here, we discuss our current understanding of how neuronal and glial development affects CNS angiogenesis and barriergenesis, and outline future directions to elucidate how neuronal activity might influence these processes. An understanding of these mechanisms is crucial for developing new interventions to treat neurovascular pathologies.

Fgfbp1 promotes blood-brain barrier development by regulating collagen IV deposition and maintaining Wnt/ß-catenin signaling.

Central nervous system (CNS) blood vessels contain a functional blood-brain barrier (BBB) that is necessary for neuronal survival and activity. Although Wnt/ß-catenin signaling is essential for BBB development, its downstream targets within the neurovasculature remain poorly understood. To identify targets of Wnt/ß-catenin signaling underlying BBB maturation, we performed a microarray analysis that identified Fgfbp1 as a novel Wnt/ß-catenin-regulated gene in mouse brain endothelial cells (mBECs). Fgfbp1 is expressed in the CNS endothelium and secreted into the vascular basement membrane during BBB formation. Endothelial genetic ablation of Fgfbp1 results in transient hypervascularization but delays BBB maturation in specific CNS regions, as evidenced by both upregulation of Plvap and increased tracer leakage across the neurovasculature due to reduced Wnt/ß-catenin activity. In addition, collagen IV deposition in the vascular basement membrane is reduced in mutant mice, leading to defective endothelial cell-pericyte interactions. Fgfbp1 is required cell-autonomously in mBECs to concentrate Wnt ligands near cell junctions and promote maturation of their barrier properties in vitro Thus, Fgfbp1 is a crucial extracellular matrix protein during BBB maturation that regulates cell-cell interactions and Wnt/ß-catenin activity.

Findings on Repeat Posttraumatic Brain Computed Tomography Scans in Older Patients With Minimal Head Trauma and the Impact of Existing Antithrombotic Use.

STUDY OBJECTIVE: Evaluate the utility of routine rescanning of older, mild head trauma patients with an initial negative brain computed tomography (CT), who is on a preinjury antithrombotic (AT) agent by assessing the rate of delayed intracranial hemorrhage (dICH), need for surgery, and attributable mortality. METHODS: Participating centers were trained and provided data collection instruments per institutional review board-approved protocols. Data were obtained from manual chart review and electronic medical record download. Adults ≥55 years seen at Level I/II Trauma Centers, between 2017 and 2019 with suspected head trauma, Glasgow Coma Scale 14 to 15, negative initial brain CT, and no other Abbreviated Injury Scale injuries >2 were identified, grouped by preinjury AT therapy (AT- or AT+) and compared on dICH rate, need for operative neurosurgical intervention, and attributable mortality using univariate analysis (α=.05). RESULTS: A total of 2,950 patients from 24 centers were enrolled; 280 (9.5%) had a repeat brain CT. In those rescanned, the dICH rate was 15/126 (11.9%) for AT- and 6/154 (3.9%) in AT+. Assuming nonrescanned patients did not suffer clinically meaningful dICH, the dICH rate would be 15/2001 (0.7%) for AT- and 6/949 (0.6%) for AT+. No surgical operations were done for dICH. All-cause mortality was 9/2950 (0.3%) and attributable mortality was 1/2950 (0.03%). The attributable death was an AT+, dICH patient whose family declined intervention. CONCLUSION: In older patients with an initial Glasgow Coma Scale of 14 to 15 and a negative initial brain CT scan, the dICH rate is low (<1%) and of minimal clinical consequence, regardless of AT use. In addition, no patient had operative neurosurgical intervention. Therefore, routine rescanning is not supported based on the results of this study.

Predicting Complicated Mild Traumatic Brain Injury in Adolescent Trauma to Enhance Clinical Decisions in Imaging.

BACKGROUND: The Pediatric Emergency Care Applied Research Network (PECARN) traumatic brain injury algorithm is used to identify children at low risk of clinically significant traumatic brain injuries to reduce computed tomography (CT) exposure. Adapting PECARN rules based on population-specific risk stratification has been suggested to improve diagnostic accuracy. OBJECTIVE: This study sought to identify center-specific patient variables, beyond PECARN rules, that may enhance the identification of patients requiring neuroimaging. METHODS: This single-center, retrospective cohort study was conducted from July 1, 2016, to July 1, 2020, in a Southwestern U.S. Level II pediatric trauma center. The inclusion criteria were adolescents (10-15 years), Glasgow Coma Scale (13-15), with a confirmed mechanical blow to the head. Patients without a head CT were excluded. Logistic regression was performed to identify additional complicated mild traumatic brain injury predictor variables beyond the PECARN. RESULTS: There were 136 patients studied; 21 (15%) presented with a complicated mild traumatic brain injury. Relative to motorcycle collision or all-terrain vehicle trauma (odds ratio [OR] 211.75, 95% confidence interval, CI [4.51, 9931.41], p < .001), an unspecified mechanism (OR 42.0, 95% CI [1.30, 1350.97], p = .03) and consult activation (OR 17.44, 95% CI [1.75, 173.31], p = .01) were significantly associated with complicated mild traumatic brain injury. CONCLUSIONS: We identified additional factors associated with complex mild traumatic brain injury, including motorcycle collision and all-terrain vehicle trauma, unspecified mechanism, and consult activation that are not in the PECARN imaging decision rule. Adding these variables may aid in determining the need for appropriate CT scanning.

Diet and nutrition: An important risk factor in leprosy.

Leprosy, once considered as poor man's disease may cause severe neurological complications and physical disabilities. Classification of leprosy depends upon the cell mediated and humoral immune responses of the host, from tuberculoid to lepromatous stage. Current therapy to prevent the disease is not only very lengthy but also consists of expensive multiple antibiotics in combination. Treatment and the duration depend on the bacillary loads, from six months in paucibacillary to a year in multibacillary leprosy. Although as per WHO recommendations, these antibiotics are freely available but still out of reach to patients of many rural areas of the world. In this review, we have focused on the nutritional aspect during the multi-drug therapy of leprosy along with the role of nutrition, particularly malnutrition, on susceptibility of Mycobacterium leprae and development of clinical symptoms. We further discussed the diet plan for the patients and how diet plans can affect the immune responses during the disease.

Laminin-dystroglycan signaling regulates retinal arteriogenesis.

Proper arteriovenous morphogenesis is crucial for maintaining normal tissue perfusion. However, our understanding of how arterial morphogenesis is regulated in the CNS is incomplete. In this study, we asked whether vascular basement membrane (BM) laminins, specifically the γ3-containing isoforms, regulate retinal arterial morphogenesis. We provide evidence that Laminin-γ3 is deposited at both arterial and venous BMs during arteriogenesis. Vascular BM Laminin-γ3 bound dystroglycan (DG), a laminin receptor preferentially expressed by arterial endothelial cells (ECs) during arteriogenesis. Blockade of laminin-DG binding in vitro led to decreased Delta-like ligand (DLL)-4 expression in ECs. Moreover, genetic deletion of the Laminin-γ3- and EC-specific deletion of DG led to similar defects in retinal arteriogenesis, including reduced Dll4 expression, hyperbranching and reduced smooth muscle coverage. These results implicate a newly identified Laminin-γ3-DG signaling cascade that regulates arterial Dll4/Notch signaling to specify and stabilize retinal arteries.-Biswas, S., Watters, J., Bachay, G., Varshney, S., Hunter, D. D., Hu, H., Brunken, W. J. Laminin-dystroglycan signaling regulates retinal arteriogenesis.

Laminin-Dependent Interaction between Astrocytes and Microglia: A Role in Retinal Angiogenesis.

Retinal vascular diseases are among the leading causes of acquired blindness. In recent years, retinal microglia have been shown to influence vascular branching density and endothelial cell proliferation. However, how microglial recruitment and activation are regulated during development remains unclear. We hypothesized that microglial recruitment, activation, and down-stream signaling are modulated by components of the mural basement membrane. We used a reverse genetic approach to disrupt laminin expression in the vascular basement membrane and demonstrate that microglia respond to the mural basement membrane in an isoform-specific manner. Microglial density is significantly increased in the laminin γ3-null (Lamc3-/-) retinal superficial vascular plexus and consequently the vascular branching density is increased. Microglia also respond to astrocyte-derived matrices and become hyperactivated in the Lamc3-/- retina or when tested in vitro with cell-derived matrix. Pharmacological activation of microglia in the wild-type retina produced an Lamc3-/--like vascular phenotype, whereas pharmacological blocking of microglial activation in the Lamc3-/- retina rescued the wild-type vascular phenotype. On the molecular level, microglial transforming growth factor-ß1 expression is down-regulated in the Lamc3-/- retina, and SMAD signaling decreased in endothelial cells with a consequent increase in endothelial proliferation. The reverse effects were seen in the Lamb2-/- retina. Together, our results demonstrate a novel mechanism by which laminins modulate vascular branching and endothelial cell proliferation during retinal angiogenesis.

Dehydration of the Uranyl Peroxide Studtite, [UO2(η2-O2)(H2O)2]·2H2O, Affords a Drastic Change in the Electronic Structure: A Combined X-ray Spectroscopic and Theoretical Analysis.

The minerals studtite, [UO2(η2-O2)(H2O)2]·2H2O, and metastudtite, [UO2(η2-O2)(H2O)2], are uranyl peroxide minerals that are major oxidative alteration phases of UO2 under conditions of geological storage. The dehydration of studtite has been studied using X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy. XPS of the U 4f region shows small but significant differences between studtite and metastudtite, with the 4f binding energy of studtite being the highest reported for a uranyl mineral studied by this technique. Further information about the changes in the electronic structure was elucidated using U M4-edge high-energy resolution X-ray absorption near-edge structure (HR-XANES) spectroscopy, which directly probes f orbital states. The transition from the 3d to 5fσ* orbital is sensitive to variations in the U═Oaxial bond length and to changes in the bond covalency. We report evidence that the covalence in the uranyl fragment decreases upon dehydration. Photoluminescence spectroscopy at near-liquid helium temperatures reveals significant spectral differences between the two materials, correlating with the X-ray spectroscopy results. A theoretical investigation has been conducted on the structures of both studtite and metastudtite and benchmarked to the HR-XANES spectra. These illustrate the sensitivity of the 3d to 5f σ* transition toward U═Oaxial bond variation. Small structural changes upon dehydration have been shown to have an important electronic effect on the uranyl fragment.

Structural Variability of 4f and 5f Thiocyanate Complexes and Dissociation of Uranium(III)-Thiocyanate Bonds with Increased Ionicity.

A series of complexes [Et4N][Ln(NCS)4(H2O)4] (Ln = Pr, Tb, Dy, Ho, Yb) have been structurally characterized, all showing the same structure, namely a distorted square antiprismatic coordination geometry, and the Ln-O and Ln-N bond lengths following the expected lanthanide contraction. When the counterion is Cs+, a different structural motif is observed and the eight-coordinate complex Cs5[Nd(NCS)8] isolated. The thorium compounds [Me4N]4[Th(NCS)7(NO3)] and [Me4N]4[Th(NCS)6(NO3)2] have been characterized, and high coordination numbers are also observed. Finally, attempts to synthesize a U(III) thiocyanate compound has been unsuccessful; from the reaction mixture, a heterocycle formed by condensation of five MeCN solvent molecules, possibly promoted by U(III), was isolated and structurally characterized. To rationalize the inability to isolate U(III) thiocyanate compounds, thin-layer cyclic voltammetry and IR spectroelectrochemistry have been utilized to explore the cathodic behavior of [Et4N]4[U(NCS)8] and [Et4N][U(NCS)5(bipy)2] along with a related uranyl compound [Et4N]3[UO2(NCS)5]. In all examples, the reduction triggers a rapid dissociation of [NCS]- ions and decomposition. Interestingly, the oxidation chemistry of [Et4N]3[UO2(NCS)5] in the presence of bipy gives the U(IV) compound [Et4N]4[U(NCS)8], an unusual example of a ligand-based oxidation triggering a metal-based reduction. The experimental results have been augmented by a computational investigation, concluding that the U(III)-NCS bond is more ionic than the U(IV)-NCS bond.

Laminins containing the ß2 and γ3 chains regulate astrocyte migration and angiogenesis in the retina.

Pathologies of retinal blood vessels are among the major causes of blindness worldwide. A key cell type that regulates retinal vascular development is the astrocyte. Generated extrinsically to the retina, astrocytes migrate into the retina through the optic nerve head. Even though there is a strong correlation between astrocyte distribution and retinal vascular development, the factors that guide astrocytes into the retina remain unclear. In this study, we show that astrocytes migrate within a laminin-containing basement membrane - the inner limiting membrane. Genetic deletion of the laminin ß2 and γ3 chains affects astrocyte migration and spatial distribution. We show that laminins act as haptotactic factors in vitro in an isoform-specific manner, inducing astrocyte migration and promoting astrocyte differentiation. The addition of exogenous laminins to laminin-null retinal explants rescues astrocyte migration and spatial patterning. Furthermore, we show that the loss of laminins reduces ß1 integrin expression in astrocytes. Culturing laminin-null retinal astrocytes on laminin substrates restores focal localization of ß1 integrin. Finally, we show that laminins containing ß2 and γ3 chains regulate subsequent retinal blood vessel growth and maintain vascular integrity. These in vivo and in vitro studies demonstrate clearly that laminins containing ß2 and γ3 chains are indispensable for migration and spatial organization of astrocytes and that they play a crucial role during retinal angiogenesis in vivo.

Supramolecular 2D/3D isomerism in a compound containing heterometallic Cu(II)2Co(II) nodes and dicyanamide bridges.

Three new heterometallic copper(II)-cobalt(II) complexes [(CuL(2))2Co{dca}2]·H2O(1), [(CuL(1))2Co{dca}2]n (2a), and [(CuL(1))2Co{dca}2]n (2b) [dca(-) = dicyanamide = N(CN)2(-)] have been synthesized by reacting the "metallo-ligand" [CuL(1)] or [CuL(2)] with cobalt(II) perchlorate and sodium dicyanamide in methanol-water medium (where H2L(1) = N,N'-bis(salicylidene)-1,3-propanediamine and H2L(2) = N,N'-bis(α-methylsalicylidene)-1,3-propanediamine). The three complexes have been structurally and magnetically characterized. Complex 1 is a discrete trinuclear species in which two metallo-ligands coordinate to a cobalt(II) ion through the phenoxido oxygen atoms along with two terminally coordinated dicyanamide ions. On the other hand, complexes 2a and 2b are one of the very scarce examples of supramolecular isomers since they present the same [(CuL(1))2Co{dca}2] trinuclear units (very similar to the trinuclear core in 1) and differ only in their superstructures. Thus, although each Cu2Co trimer in 2a and 2b is connected to four other Cu2Co trimers through four µ1,5-dca(-) bridges, 2a presents a square two-dimensional structure (each Cu2Co trimer is connected to four in-plane Cu2Co trimers); whereas, 2b shows a triangular three-dimensional lattice (each Cu2Co trimer is connected to three in-plane and one out-of-plane trimers). Variable-temperature magnetic susceptibility measurements show the presence of moderate antiferromagnetic exchange interactions (ferrimagnetic) in all the cases mediated through the double phenoxido bridges that have been fitted with an anisotropic model including spin-orbit coupling in the central Co(II) ion.

Double Trouble: Exploring Bilateral Acetabular Fractures in a Trauma Patient.

Bilateral acetabular fractures, though rare, pose significant challenges in both diagnosis and management due to their association with high-energy trauma and the potential for long-term disability. This case report presents the clinical course of a 27-year-old female who presented to our department after a motorcycle accident with bilateral acetabular fractures. Initial assessment revealed nondisplaced bilateral acetabular fractures, along with associated injuries including a right ulnar styloid fracture. Further evaluation via 3D CT scan delineated associated column fractures on the right and posterior + anterior wall fractures on the left, classified according to the Letournel and Judet system. Notably, this specific combination of acetabular fractures has not been documented in existing literature as per our investigation. The surgical intervention involved an anterior intrapelvic approach for open reduction and internal fixation (ORIF) of the right acetabulum, while the left acetabulum was managed conservatively. Postoperatively, the patient is scheduled for non-weightbearing activity until radiographic evidence of fracture healing is observed. This case underscores the importance of tailored surgical approaches and comprehensive management strategies in optimizing outcomes for patients with bilateral acetabular fractures.

Successful Coil Embolization of Active Bleeding From a Replaced Left Hepatic Artery to the Left Gastric Artery Associated With a Traumatic Rupture of a Simple Hepatic Cyst Causing Hemodynamic Instability.

Intra-abdominal hemorrhage resulting from a ruptured, large hepatic cyst in a polycystic liver disease (PCLD) patient is rare and potentially fatal if not addressed promptly. Only a few isolated cases have previously been reported. The usual patient profile consists of elderly patients on anticoagulation, as is demonstrated in our case. Intra-hepatic cysts are broadly classified into congenital, traumatic, infectious, parasitic, and neoplastic. Congenital intra-hepatic cysts can consist of both simple and PCLD, as is outlined in our case. Simple cysts are usually asymptomatic, but occasionally they may achieve larger dimensions and lead to complications such as rupture, obstruction, infection, hemorrhage, and even portal hypertension. We present an uncommon case of a 78-year-old patient with PCLD on rivaroxaban who presented initially with diffuse abdominal pain, distension, and progression into hemodynamic instability. A computerized tomography (CT) scan revealed a ruptured left hepatic lobe cyst, causing hemoperitoneum and resulting in an acute abdomen. This case was complicated by the patient's anticoagulation status and anomalous hepatic vasculature pattern. Interventional radiology (IR) successfully identified the aberrant bleeding vessel and stopped the active extravasation with super-selective coil embolization.

Necrotizing Fasciitis Masquerading as Stroke: A Diagnostic Dilemma.

Necrotizing fasciitis (NF) poses a diagnostic challenge due to its rarity and similarity in presentation with other critical conditions. We report a case of a 79-year-old male who initially presented with altered mental status and stroke-like symptoms; he was ultimately diagnosed with abdominal wall NF spreading to the lower extremity. Despite a history of cecal mass perforation noted in prior imaging, the patient had been discharged from an outside emergency room on antibiotics, highlighting a missed opportunity for early intervention. Subsequent deterioration led to sepsis, organ failure, and ultimately, the detection of NF. Prompt recognition of subtle skin changes and laboratory abnormalities, along with a detailed physical examination, is essential for a timely and accurate diagnosis. Surgical debridement, coupled with broad-spectrum antibiotics, remains the cornerstone of treatment. Delays in surgical management significantly increase mortality, emphasizing the importance of prompt diagnosis and intervention. This case underscores the necessity for heightened awareness among healthcare providers to recognize NF promptly, especially when its clinical presentation overlaps with other critical conditions. Multidisciplinary collaboration and continued education are imperative to improve outcomes and prevent delays in the diagnosis and treatment of NF.

Glutamatergic neuronal activity regulates angiogenesis and blood-retinal barrier maturation via Norrin/ß-catenin signaling.

Interactions among neuronal, glial and vascular components are crucial for retinal angiogenesis and blood-retinal barrier (BRB) maturation. Although synaptic dysfunction precedes vascular abnormalities in many retinal pathologies, how neuronal activity, specifically glutamatergic activity, regulates retinal angiogenesis and BRB maturation remains unclear. Using in vivo genetic studies in mice, single-cell RNA-sequencing and functional validation, we show that deep plexus angiogenesis and paracellular BRB maturation are delayed in Vglut1 -/- retinas where neurons fail to release glutamate. In contrast, deep plexus angiogenesis and paracellular BRB maturation are accelerated in Gnat1 -/- retinas where constitutively depolarized rods release excessive glutamate. Norrin expression and endothelial Norrin/ß-catenin signaling are downregulated in Vglut1 -/- retinas, and upregulated in Gnat1 -/- retinas. Pharmacological activation of endothelial Norrin/ß-catenin signaling in Vglut1 -/- retinas rescued defects in deep plexus angiogenesis and paracellular BRB maturation. Our findings demonstrate that glutamatergic neuronal activity regulates retinal angiogenesis and BRB maturation by modulating endothelial Norrin/ß-catenin signaling.

Glutamatergic neuronal activity regulates angiogenesis and blood-retinal barrier maturation via Norrin/ß-catenin signaling.

Interactions among neuronal, glial, and vascular components are crucial for retinal angiogenesis and blood-retinal barrier (BRB) maturation. Although synaptic dysfunction precedes vascular abnormalities in many retinal pathologies, how neuronal activity, specifically glutamatergic activity, regulates retinal angiogenesis and BRB maturation remains unclear. Using in vivo genetic studies in mice, single-cell RNA sequencing (scRNA-seq), and functional validation, we show that deep plexus angiogenesis and paracellular BRB maturation are delayed in Vglut1-/- retinas where neurons fail to release glutamate. By contrast, deep plexus angiogenesis and paracellular BRB maturation are accelerated in Gnat1-/- retinas, where constitutively depolarized rods release excessive glutamate. Norrin expression and endothelial Norrin/ß-catenin signaling are downregulated in Vglut1-/- retinas and upregulated in Gnat1-/- retinas. Pharmacological activation of endothelial Norrin/ß-catenin signaling in Vglut1-/- retinas rescues defects in deep plexus angiogenesis and paracellular BRB maturation. Our findings demonstrate that glutamatergic neuronal activity regulates retinal angiogenesis and BRB maturation by modulating endothelial Norrin/ß-catenin signaling.

A new family of trinuclear nickel(II) complexes as single-molecule magnets.

Three new trinuclear nickel (II) complexes with the general composition [Ni3 L3 (OH)(X)](ClO4 ) have been prepared in which X=Cl(-) (1), OCN(-) (2), or N3(-) (3) and HL is the tridentate N,N,O donor Schiff base ligand 2-[(3-dimethylaminopropylimino)methyl]phenol. Single-crystal structural analyses revealed that all three complexes have a similar Ni3 core motif with three different types of bridging, namely phenoxido (µ2 and µ3 ), hydroxido (µ3 ), and µ2 -Cl (1), µ1,1 -NCO (2), or µ1,1 -N3 (3). The nickel(II) ions adopt a compressed octahedron geometry. Single-crystal magnetization measurements on complex 1 revealed that the pseudo-three-fold axis of Ni3 corresponds to a magnetic easy axis, being consistent with the magnetic anisotropy expected from the coordination structure of each nickel ion. Temperature-dependent magnetic measurements indicated ferromagnetic coupling leading to an S=3 ground state with 2J/k=17, 17, and 28 K for 1, 2, and 3, respectively, with the nickel atoms in an approximate equilateral triangle. The high-frequency EPR spectra in combination with spin Hamiltonian simulations that include zero-field splitting parameters DNi /k=-5, -4, and -4 K for 1, 2, and 3, respectively, reproduced the EPR spectra well after a anisotropic exchange term was introduced. Anisotropic exchange was identified as Di,j /k=-0.9, -0.8, and -0.8 K for 1, 2, and 3, respectively, whereas no evidence of single-ion rhombic anisotropy was observed spectroscopically. Slow relaxation of the magnetization at low temperatures is evident from the frequency-dependence of the out-of-phase ac susceptibilities. Pulsed-field magnetization recorded at 0.5 K shows clear steps in the hysteresis loop at 0.5-1 T, which has been assigned to quantum tunneling, and is characteristic of single-molecule magnets.

Use of metalloligands [CuL] (H2L = salen type di-Schiff bases) in the formation of heterobimetallic copper(II)-uranyl complexes: photophysical investigations, structural variations, and theoretical calculations.

Five heterobimetallic copper(II)-uranium(VI) complexes [(CuL(1))UO2(NO3)2] (1), [{CuL(1)(CH3CN)}UO2(NO3)2] (2), [{CuL(1)(CH3COCH3)}UO2(NO3)2] (3), [{CuL(2)(CH3CN)}UO2(NO3)2](4), and [{CuL(2)(CH3COCH3)}UO2(NO3)2][{CuL(2)}UO2(NO3)2] (5) have been synthesized by reacting the Cu(II)-derived metalloligands [CuL(1)] and [CuL(2)] (where, H2L(1) = N,N'-bis(α-methylsalicylidene)-1,3-propanediamine and H2L(2) = N,N'-bis(salicylidene)-1,3-propanediamine) with UO2(NO3)2·6H2O in 1:1 ratio by varying the reaction temperature and solvents. Absorption and fluorescence quenching experiments (steady-state and time-resolved) indicate the formation of 1:1 ground-state charge transfer copper(II)-uranium(VI) complexes in solution. X-ray single-crystal structure reveals that each complex contains diphenoxido bridged Cu(II)-U(VI) dinuclear core with two chelated nitrato coligands. The complexes are solvated (acetonitrile or acetone) in the axial position of the Cu(II) in different manner or desolvated. The supramolecular interactions that depend upon the co-ordinating metalloligands seem to control the solvation. In complexes 2 and 3 a rare NO3(-)···NO3(-) weak interaction plays an important role in forming supramolecular network whereas an uncommon U═O···NO3(-) weak interaction helps to self-assemble heterobinuclear units in complex 5. The significance of the noncovalent interactions in terms of energies and geometries has been analyzed using theoretical calculations.