Surface Engineering of Atomically Precise M(I) Nanoclusters: From Structural Control to Room Temperature Photoluminescence Enhancement.

ConspectusUnderstanding the structural architecture of nanoparticles is essential for investigating their fundamental properties because these materials have become more desirable in modern nanoscience research. Designing a proper synthetic strategy to control their growth with atomic precision is crucial. The polydispersed nature of the nanoparticles makes determining their precise structural information challenging. Metal nanoclusters (NCs) have emerged as a promising solution to this problem as they bridge the gap between metal nanoparticles and discrete molecular complexes. Well-ordered molecular structures provide opportunities to look at structure-property correlations and find quantum confinement effects at the atomic level that reveal their similarity to molecular-like properties. While most M(0)/(I)-based NCs exhibit exceptional photoluminescence (PL) emission at room temperature, M(I)-based NCs are less likely to exhibit PL emissions due to their electronic environment. Developments in the field of metal nanoparticles have made it intriguing to achieve room-temperature PL emission in M(I) NCs. Efforts have focused on developing efficient methods for preparing luminescent M(I) NCs to better comprehend fundamental aspects of their PL emission properties. We provide an overview of various synthetic strategies for preparing NCs and their selective functionalization for generating room-temperature PL emissions. Our focus has been creating an Ag(I) NC with a core-shell architecture, as this unique structural design complements the charge transition phenomenon. The molecular structure obtained from single-crystal X-ray diffraction (SCXRD) and associated theoretical calculation revealed that our effort results in a unique hexagonal closed pack core and Keplerate shell containing [S@Ag50S12(StBu)20]4+ NC where the charge transition between the core and the metal-ligand shell facilitates emission properties. We also explored the approach of host-guest supramolecular adduct formations to engineer the surface of ligands that reduce nonradiative relaxation rates by restricting surface molecular vibrations and controlling the generation of PL emission. To do this, we capped precisely structured [Cl@Ag16S(S-Adm)8(CF3COO)5(DMF)3(H2O)2]·DMF with ß-cyclodextrin via adamantane moieties. We also describe the effects of bimetallic cluster formation on increasing surface rigidity and modulating the frontier molecular orbital arrangement, which helps to attain synergy to generate room-temperature PL emission. We focused on the structural integrity of Ag(I) NCs, allowing us to incorporate heterometal atoms at peripheral positions that lead to the formation of [CO2@Ag20Cu2S2(StBu)10(CF3COO)8(DMA)4]·(DMA). We also explored the impact of introducing extra ligands into the Ag(I) cluster node on the generation of PL emission at room-temperature. These strategies are not limited to Ag NCs. We discussed the possibility of combining core-shell architecture and surface modifications to enhance PL emission in [Cu18H3(S-Adm)12(PPh3)4Cl2] NC at room temperature. SCXRD studies revealed its distinct core-shell architecture that ensures electronic transitions and that transition is controlled by the imposed surface rigidity that yields a higher PL emission. We believe that this innovative structural engineering holds potential for the advancement of NC research, and this Account will inspire the scientific community to synthesize functional M(I) NCs.

Anomalous Aharonov-Bohm Interference in the Presence of Edge Reconstruction.

Interferometry is a vital tool for studying fundamental features in the quantum Hall effect. For instance, Aharonov-Bohm interference in a quantum Hall interferometer can probe the wave-particle duality of electrons and quasiparticles. Here, we report an unusual Aharonov-Bohm interference of the outermost edge mode in a quantum Hall Fabry-Pérot interferometer, whose Coulomb interactions were suppressed with a grounded drain in the interior bulk of the interferometer. In a descending bulk filling factor from ν_{b}=3 to ν_{b}≈(5/3), the magnetic field periodicity, which corresponded to a single "flux quantum," agreed accurately with the enclosed area of the interferometer. However, in the filling range, ν_{b}≈(5/3) to ν_{b}=1, the field periodicity increased markedly, a priori suggesting a drastic shrinkage of the Aharonov-Bohm area. Moreover, the modulation gate voltage periodicity decreased abruptly at this range. We attribute these unexpected observations to edge reconstruction, leading to area changing with the field and a modified modulation gate-edge capacitance. These reproducible results support future interference experiments with a quantum Hall Fabry-Pérot interferometer.

Silver Cluster Assembled Materials: A Model-Driven Perspective on Recent Progress, with a Spotlight on Ag12 Cluster Assembly.

The exploration of individual nanoclusters is rapidly advancing, despite stability concerns. To address this challenge, the assembly of cluster nodes through linker molecules has been successfully implemented. However, the linking of the cluster nodes itself introduces a multitude of possibilities, especially when additional factors come into play. While this method proves effective in enhancing material stability, the specific reasons behind its success remain elusive. In our laboratory, we have undertaken extensive studies on Ag cluster-assembled materials. So, here our goal is to establish a model system that allows for the discernment of various factors, eliminating unnecessary complexities during the linking approach. So, we hope that the systematic discourse presented in here will contribute significantly to future endeavors, helping to set clear priorities, and provide solutions to concerns that arise when working with a model system.

The presence and burden of cognitive issues: discordance between the perception of neurologists and people living with multiple sclerosis.

BACKGROUND AND PURPOSE: Cognitive impairment is a common symptom of multiple sclerosis (MS) and occurs in more than 40% of people living with MS (plwMS). No real-world study has assessed the perception of neurologists and plwMS on cognitive issues. METHODS: Using data from the 2011-2019 Adelphi MS Disease Specific Programme database, this real-world, retrospective, cross-sectional multi-cohort study included people aged ≥18 years with relapsing-remitting MS and secondary progressive MS from the United States, UK and the EU. Neurologists provided data on the patient record form for plwMS, with the same plwMS invited to voluntarily complete a patient self-completion form: a questionnaire about their experiences with MS. RESULTS: Of 25,374 plwMS, 4817 who provided information on cognitive and mood symptoms were included in the analysis. Of the plwMS, 68% and 59% reported feeling 'mentally fatigued' and having 'difficulty concentrating', respectively. Neurologists reported only 27% of plwMS as having 'difficulty concentrating' and 15% of plwMS as having 'short-/long-term memory problems'. Neurologists reported cognitive or mood symptoms as 'not experienced' by a higher percentage of participants with relapsing-remitting MS than secondary progressive MS. Of the plwMS who experienced 'difficulty concentrating', most had a concomitant feeling of being 'mentally fatigued' (52%), followed by 'feeling anxious or tense' (49%) and 'feeling depressed' (44%). In plwMS, caregivers reported 'difficulty concentrating' (16%) as the most common cognitive issue. CONCLUSION: A clear discordance was observed between neurologists and plwMS regarding the perception of the cognitive and neuropsychiatric issues. These results underline the under-perception of cognitive and emotional affective symptoms in plwMS during neurological consultations.

Two-Dimensional Silver-Chalcogenolate-Based Cluster-Assembled Material: A p-type Semiconductor.

We have synthesized and characterized a new two-dimensional honeycomb architecture resembling a single-layer of atomically precise silver cluster-assembled material (CAM), [Ag12(StBu)6(CF3COO)6(4,4'-azopyridine)3] (Ag12-azo-bpy). The interlayer noncovalent van der Waals interactions within the single-crystals were successfully disrupted, leading to the creation of this unique structure. The optimized Ag12-azo-bpy CAM demonstrates a valence band that is localized on the Ag12 cluster node situated near the Fermi energy level. This localization induces electron injection from the linker to the cluster node, facilitating efficient charge transportation along the plane. Exploiting this single-layer structure as a distinctive platform for p-type channel material, it was employed in a field-effect transistor configuration. Remarkably, the transistor exhibits a high hole mobility of 1.215 cm2 V-1 s-1 and an impressive ON/OFF current ratio of ∼4500 at room-temperature.

Electron Pairing of Interfering Interface-Based Edge Modes.

The remarkable Cooper-like pairing phenomenon in the Aharonov-Bohm interference of a Fabry-Perot interferometer-operating in the integer quantum Hall regime-remains baffling. Here, we report the interference of paired electrons employing "interface edge modes." These modes are born at the interface between the bulk of the Fabry-Perot interferometer and an outer gated region tuned to a lower filling factor. Such a configuration allows toggling the spin and the orbital of the Landau level of the edge modes at the interface. We find that electron pairing occurs only when the two modes (the interfering outer and the first inner) belong to the same spinless Landau level.

Shedding Novel Photophysical Insights Toward Discriminative Detection of Three Toxic Heavy Metal Ions and a hazard class 1 nitro-explosive By Using a Simple AIEE Active Luminogen.

In this work, we introduced a simple aggregation-induced emission enhancement (AIEE) sensor (PHCS) which can selectively detect and discriminate three environmentally and biologically imperative heavy metal ions (Cu2+, Co2+ and Hg2+) and a hazard class 1 categorized nitro-explosive picric acid (PA) in differential media. By virtue of its weak fluorescence attributes in pure organic medium owing to the synergistic operation of multiple photophysical quenching mechanisms, the molecular probe showcased highly selective 'TURN ON' fluorogenic response towards hazardous Hg2+ with a limit of detection (LOD) as low as 97 nM. Comprehensive investigation of binding mechanism throws light on the cumulative effect of probe-metal complexation induced chelation enhanced fluorescence (CHEF) effect and subsequent AIEE activation within the formed probe-metal adducts. Noteworthily, the probe (PHCS) can be readily used in real water samples for the quantitative determination of Hg2+ in a wide concentration range. In addition, the probe displayed modest colorimetric recognition performances to selectively detect and discriminate two essential heavy metal ions (Cu2+ and Co2+) with a LOD of 96 nM and 65 nM for Cu2+ and Co2+ respectively, in semi-aqueous medium. Intriguingly, based on high photoluminescence efficiency, the AIEE active nano-aggregated PHCS displayed a remarkable propensity to be used as a selective and ultra-sensitive 'TURN-OFF' fluorogenic chemosensor towards PA with LOD of 34.4 ppb in aqueous medium. Finally, we specifically shed light on the interaction of PHCS hydrosol towards PA using some unprecedented techniques, which helped uncover new photophysical insights of probe-explosive molecule interaction. We shed light on novel photophysical insights toward unique multifunctional sensory aptitude of a simple aggregation-induced emission enhancement active organic functional molecule in differential media, enabling ultra-sensitive discriminative detection of toxic heavy metal ions and explosive molecule simultaneously.

Marginalised social groups differentials in nutritional status (BMI) among reproductive-aged women in West Bengal.

BACKGROUND: SCs and STs, historically marginalized communities in India, have been subjected to social and economic discrimination for centuries. Despite affirmative action policies, these communities face systemic discrimination and exclusion in various aspects of their lives. Poor health conditions among SC and ST women are caused by insufficient consumption of nutritious food, leading to undernutrition and related health issues. To address gaps in the literature regarding the nutritional status of these women, this study aims to compare the BMI of SC and ST women in West Bengal and investigate the factors affecting their BMI. The study's findings can inform targeted interventions to improve the nutritional status of SC and ST women in West Bengal and reduce disparities in their health outcomes. MATERIALS AND METHODS: This study analyzed data from the National Family Health Survey (NFHS-5) to examine the distribution of underweight and  non-underweight SC and ST women in West Bengal. The sample included 5,961 non-pregnant reproductive-aged SC women and 1,496 non-pregnant reproductive-aged ST women. A binary logistic regression model was used to determine how background characteristics affect the nutritional status (BMI) of respondents, while a multivariate decomposition analysis was conducted to identify the covariates contributing to the nutritional status difference between SC and ST women. QGIS 2.18.25 software was utilized to map the spatial distribution of underweight and non-underweight SC and ST reproductive-aged women. RESULTS: This study examines the nutritional status and differential background characteristics among SC and ST women in West Bengal, India. Results show that undernutrition affects the ST population more than the SC population, with age, marital status, religion, place of residence, educational status, and wealth quintile being significant factors affecting nutritional status. Food and dietary habits also impact nutritional status, with milk or curd, pulses or beans, dark green leafy vegetables, eggs, and fish being associated with lower rates of underweight. Binary logistic regression analysis reveals significant associations between socio-demographic factors and underweight status among SC and ST women. Socio-demographic factors were found to be the major contributors to the gap between SC and ST women, followed by food and dietary factors. The study highlights the need for targeted interventions to improve the nutritional status of marginalized communities like SC and ST women in West Bengal. CONCLUSION: The study highlights a significant population suffering from underweight in West Bengal, with socio-economic factors and dietary habits significantly contributing to the nutritional gap between SC and ST reproductive-aged women. Policy implications suggest targeted interventions to improve access to education and employment opportunities and promote a healthy and balanced diet to reduce the gap. Future studies could explore vulnerability risks of these domains.

The New Ag-S Cluster [Ag50S13(StBu)20][CF3COO]4 with a Unique hcp Ag14 Kernel and Ag36 Keplerian-Shell-Based Structural Architecture and Its Photoresponsivity.

In metal nanoclusters (NCs), the kernel geometry and the nature of the surface protecting ligands are very crucial for their structural stability and properties. The synthesis and structural elucidation of Ag NCs is challenging because the zerovalent oxidation state of Ag is very reactive and prone to oxidization. Here, we report the NC [Ag50S13(StBu)20][CF3COO]4 with a hexagonal close-packed (hcp) cagelike Ag14 kernel. A truncated cubic shell and an octahedral shell encapsulate the hcp-layered kernel via an interstitial S2- anionic shell to form an Ag36 Keplerian outer shell of the NC. A theoretical study indicates the stability of this NC in its 4+ charge state and the charge distribution between the kernel and Keplerian shell. The unprecedented electronic structure facilitates its application toward sustainable photoresponse properties. The new insights into this novel Ag NC kernel and Keplerian shell structure may pave the way to understanding the unique structure and developing electronic structure-based applications.

Chemical and Electrochemical O2 Reduction on Earth-Abundant M-N-C Catalysts and Implications for Mediated Electrolysis.

M-N-C catalysts, incorporating non-precious-metal ions (e.g. M = Fe, Co) within a nitrogen-doped carbon support, have been the focus of broad interest for electrochemical O2 reduction and aerobic oxidation reactions. The present study explores the mechanistic relationship between the O2 reduction mechanism under electrochemical and chemical conditions. Chemical O2 reduction is investigated via the aerobic oxidation of a hydroquinone, in which the O-H bonds supply the protons and electrons needed for O2 reduction to water. Mechanistic studies have been conducted to elucidate whether the M-N-C catalyst couples two independent half-reactions (IHR), similar to electrode-mediated processes, or mediates a direct inner-sphere reaction (ISR) between O2 and the organic molecule. Kinetic data support the latter ISR pathway. This conclusion is reinforced by rate/potential correlations that reveal significantly different Tafel slopes, implicating different mechanisms for chemical and electrochemical O2 reduction.

India's achievement towards sustainable Development Goal 6 (Ensure availability and sustainable management of water and sanitation for all) in the 2030 Agenda.

BACKGROUND: Clean water and sanitation are global public health issues. Safe drinking water and sanitation are essential, especially for children, to prevent acute and chronic illness death and sustain a healthy life. The UN General Assembly announced the 17 Sustainable Development Goals (SDGs) and 169 targets for the 2030 Agenda on 25 September 2015. SDG 6 is very important because it affects other SDG (1, 2,3,5,11,14 and 15). The present study deals with the national and state-wise analysis of the current status and to access deficiency of India's achievement towards SDG 6 (clean water and sanitation for all) for the 2030 agenda based on targets 6.1, 6.2,6.4,6.6 from 2012 to 2020. MATERIALS AND METHODS: Data of different indicators of SDG 6 are collected from different secondary sources-NSS 69th (2012) and 76th (2018) round; CGWB annual report 2016-2017 and 2018-2019; NARSS (2019-2020); SBM-Grameen (2020). To understand overall achievement towards SDG 6 in the 2030 agenda, the goal score (arithmetic mean of normalised value) has been calculated. MAJOR FINDINGS: According to NSS data, 88.7% of Indian households had enough drinking water from primary drinking water sources throughout the year, while 79.8% of households had access to toilet facilities in 2018. As per the 2019-2021 goal score for States and UTs in rural India based on SDG 6 indicator, SDG 6 achiever States and UTs (100%) are Sikkim, Himachal Pradesh, Andaman and Nicobar Islands. CONCLUSION: Drinking water and sanitation for all ensure a healthy life. It is a matter of concern for the government, policymakers, and people to improve the condition where the goal score and indicator value of SDG 6 are low.

Rural urban differences in self-rated health among older adults: examining the role of marital status and living arrangements.

BACKGROUND: The rural-urban gap in socioeconomic and morbidity status among older adults is prevalent in India. These disparities may impact the levels and factors of self-rated health (SRH). The objective of the study is to compare the levels and determinants of SRH between rural and urban areas by considering the moderating effects of marital status and living arrangements. SUBJECTS AND METHODS: The present study used data from the Longitudinal Ageing Study in India (LASI) wave 1 (2017-18). A total sample of 30,633 older adults aged 60 years and above were selected for the study. Descriptive statistics, bivariate chi-square test, the interaction effect of living arrangements and marital status, and logistic estimation were applied to accomplish the study objectives. RESULTS: The prevalence of poor SRH was found 7% higher in rural areas compared to urban counterparts. A substantial rural-urban disparity in the patterns of poor SRH was also observed. The interaction effect of marital status and living arrangement on self-rated health suggested that older adults who were currently unmarried and living alone were 38% more likely to report poor SRH than those who were currently married and co-residing in rural India. In addition to marital status and living situation, other factors that significantly influenced SRH include age, socio-cultural background (educational attainment and religion), economic background (employment status), health status (ADLs, IADLs, multi-morbidities), and geographic background (region). CONCLUSION: The present study's findings demonstrated that, notwithstanding local variations, marital status and living circumstances significantly influenced SRH in India. In the present study, unmarried older people living alone were more susceptible to poor SRH in rural areas. The present study supports the importance of reinforcing the concepts of care and support for older individuals. There is a need for special policy attention to older individuals, particularly those unmarried and living alone. Although older individuals had difficulty performing ADLs and IADLs and had multi-morbidities, they reported poorer health. Therefore, offering them social support and top-notch medical assistance is crucial.

Solvent-Dependent Photophysical Properties of a Semiconducting One-Dimensional Silver Cluster-Assembled Material.

Unraveling the total structure of the atom-precise silver cluster-assembled materials (CAMs) is extremely significant to elucidating the structure-property correlation, but it is a very challenging task. Herein, a new silver CAM is synthesized by a facile synthetic pathway with a unique distorted elongated square-bipyramid-based Ag11 core geometry. The core is protected by two different kinds of the surface protecting ligands (adamantanethiolate and trifluoroacetate) and connected through a bidentate organic linker. The crystallographic data show that this material embraces a one-dimensional periodic structure that orchestrates by various noncovalent interactions to build a thermally stable supramolecular assembly. Further characterization confirms its n-type semiconducting property with an optical band gap of 1.98 eV. The impact of an adamantanethiol-protected silver core on the optical properties of this type of periodic framework is analyzed by the UV-vis absorbance and emission phenomena. Theoretical calculations predicted that the occupied states are majorly contributed by Ag-S. Solvent-dependent photoluminescence studies proved that a polar solvent can significantly perturb the metal thiolate and thiolate-centered frontier molecular orbitals that are involved in the electronic transitions.

Azide-Coordination in Homometallic Dinuclear Lanthanide(III) Complexes Containing Nonequivalent Lanthanide Metal Ions: Zero-Field SMM Behavior in the Dysprosium Analogue.

A series of homometallic dinuclear lanthanide complexes containing nonequivalent lanthanide metal centers [Ln2(LH2)(LH)(CH3OH)(N3)]·xMeOH·yH2O [1, Ln = DyIII, x = 0, y = 2; 2, Ln = TbIII, x = 1, y = 1] have been synthesized [LH4 = 6-((bis(2-hydroxyethyl)amino)-N'-(2-hydroxybenzylidene)picolinohydrazide] and characterized. The dinuclear assembly contains two different types of nine-coordinated lanthanide centers, because the nonequivalent binding of the azide co-ligand as well as the varying coordination of the deprotonated Schiff base ligand. Detailed magnetic studies have been performed on the complexes 1 and 2. Complex 1 and its diluted analogue (15%) are zero-field SMMs with effective energy barriers (Ueff) of magnetization reversal equal to 59(3) K and 66(3) K and relaxation times of τ0 = 10(4) × 10-6 s and 10(4) × 10-8 s, respectively. On the other hand, complex 2 shows a field-induced SMM behavior. Combined ab initio and density functional theory calculations were performed to explain the experimental findings and to unravel the nature of the magnetic anisotropy, exchange-coupled spectra, and magnetic exchange interactions between the two lanthanide centers.

Contractive Annulation: A Strategy for the Synthesis of Small, Strained Cyclophanes and Its Application in the Synthesis of [2](6,1)Naphthaleno[1]paracyclophane.

A new synthetic strategy (contractive annulation) for the synthesis of highly strained cyclophanes has been conceived and its viability has been demonstrated through a nine-step synthesis of [2](6,1)naphthaleno[1]paracyclophane from [2.2]paracyclophane.

Homometallic DyIII Complexes of Varying Nuclearity from 2 to 21: Synthesis, Structure, and Magnetism.

The synthesis, structure, and magnetic properties of four DyIII coordination compounds isolated as [Dy2 (LH2 )2 (µ2 -η1 :η1 -Piv)]Cl⋅2 MeOH⋅H2 O (1), [Dy4 (LH)2 (µ3 -OH)2 (Piv)4 (MeOH)2 ]⋅4 MeOH⋅2 H2 O (2), [Dy6 (LH2 )3 (tfa)3 (O3 PtBu)(Cl)3 ]Cl4 ⋅15.5 H2 O⋅4 MeOH⋅5 CHCl3 (3) and [Dy21 (L)7 (LH)7 (tfa)7 ]Cl7 ⋅15 H2 O⋅7 MeOH⋅12 CHCl3 (4) are reported (Piv=pivalate, tfa=1,1,1-trifluoroacetylacetone, O3 PtBu=tert-butylphosphonate). Among these, 3 displays an equilateral triangle topology with a side length of 9.541 Šand a rare pentagonal-bipyramidal Dy3+ environment, whereas complex 4 exhibits a single-stranded nanowheel structure with the highest nuclearity known for a homometallic lanthanide cluster structure. A tentative model of the dc magnetic susceptibility and the low-temperature magnetization of compounds 1 and 2 indicates that the former exhibits weak ferromagnetic intramolecular exchange interaction between the Dy3+ ions, whereas in the latter both intramolecular ferromagnetic and antiferromagnetic magnetic exchange interactions are present. Compounds 1, 3, and 4 exhibit frequency-dependent ac signals below 15 K at zero bias field, but without exhibiting any maximum above 2 K at frequencies up to 1400 Hz. The observed slow relaxation of the magnetization suggests that these compounds could exhibit single molecule magnet (SMM) behavior with either a thermal energy barrier for the reversal of the magnetization that is not high enough to block the magnetization above 2 K, or there exists quantum tunneling of the magnetization (QTM).

Luminescent Dinuclear Ruthenium Terpyridine Complexes with a Bis-Phenylbenzimidazole Spacer.

A conjugated bis-terpyridine bridging ligand, 2-(4-(2,6-di(pyridin-2-yl)pyridin-4-yl)phenyl)-6-(2-(4-(2,6-di(pyridin-2-yl)pyridin-4-yl)phenyl)-1H-benzo[d]imidazol-6-yl)-1H-benzo[d] imidazole (tpy-BPhBzimH2-tpy), was designed in this work by covalent coupling of 3,3'-diaminobenzidine and two 4'-(p-formylphenyl)-2,2':6',2″-terpyridine units to synthesize a new series of bimetallic Ru(II)-terpyridine light-harvesting complexes. Photophysical and electrochemical properties were modulated by the variation of the terminal ligands in the complexes. The new compounds were thoroughly characterized by 1H NMR spectroscopy, high-resolution mass spectrometry, and elemental analysis. Absorption spectra of the complexes consist of very strong ligand-centered π-π* and n-π* transitions in the UV, metal-to-ligand, and intraligand charge transfer bands in the visible regions. Steady-state and time-resolved emission spectral measurements indicate that the complexes exhibit moderately intense luminescence at room temperature within the spectral domain of 653-687 nm having luminescence lifetimes in the range between 6.3 and 55.2 ns, depending upon terminal tridentate ligand and solvent. Variable-temperature luminescence measurements suggest substantial increase of the energy gap between luminescent 3metal-to-ligand charge transfer state and nonluminescent 3metal centered in the complexes compared to the parent [Ru(tpy)2]2+. Each of the three bimetallic complexes exhibits only one reversible couple in the positive potential window with almost no detectable splitting corresponding to simultaneous oxidation of the two remote Ru centers. All the complexes possess a number of imidazole NH protons, which became sufficiently acidic upon metal ion coordination. By utilizing these NH protons, we thoroughly studied anion recognition properties of the complexes in pure organic as well as predominantly aqueous media through multiple optical channels and spectroscopic methods. Finally computation investigations employing density functional theory (DFT) and time-dependent DFT were done to examine the electronic structures of the complexes and accurate assignment of experimentally observed optical spectral bands.

Ullmann Reaction Catalyzed by Heterogeneous Mesoporous Copper/Manganese Oxide: A Kinetic and Mechanistic Analysis.

A heterogeneous copper oxide supported on mesoporous manganese oxide (meso Cu/MnOx) was explored for Ullmann-type cross-coupling reactions. An inverse micelle-templated evaporation-induced self-assembly method with in situ addition of copper was adopted to synthesize the mesoporous catalyst. Broad substrate scope and excellent functional group tolerability in C-O, C-N, and C-S bond formation reactions were observed using the optimized reaction conditions. The catalytic protocol was ligand free, and the catalyst was reusable without any significant loss of activity. The kinetic and Hammett analyses provided evidence for oxidative addition to a Cu(I) reaction center followed by nucleophilic addition and reductive elimination at the active copper oxide surface. Rate acceleration was observed for aryl halides with electron-withdrawing groups. The Hammett analysis determined ρ = +1.0, indicative of an oxidative addition, whereas the electronic effect in the phenol ring (ρ = -2.9) was indicative of coordination to a metal ion. Theoretically, the oxidative addition of the aryl halides is assisted by the ligand environment of the copper center. Relevant mechanistic implications are discussed on the basis of the experimental and computational results.

Mononuclear Lanthanide Complexes: Energy-Barrier Enhancement by Ligand Substitution in Field-Induced DyIII SIMs.

The sequential reaction of 2-((6-(hydroxymethyl)pyridin-2-yl)-methyleneamino)phenol (LH2), LnCl3·6H2O, and 1,1,1-trifluoroacetylacetone (Htfa) in the presence of Et3N afforded [Ln(LH) (tfa)2] [Ln = Dy3+ (1), Ln = Tb3+ (2), and Ln = Gd3+ (3)], while under the same reaction conditions, but in the absence of the coligand, another series of mononuclear complexes, namely, [Ln(LH)2]·Cl·2MeOH] [Ln = Dy3+ (4) and Tb3+ (5)] are obtained. Single-crystal X-ray diffraction analysis revealed that the former set contains a mono-deprotonated [LH]- and two tfa ligands, while the latter set comprises of two mono-deprotonated [LH]- ligands that are nearly perpendicular to each other at an angle of 86.9°. Among these complexes, 2 exhibited a ligand-sensitized lanthanide-characteristic emission. Analyses of the alternating current susceptibility measurements reveal the presence of single-molecule magnet behavior for 1 and 4, in the presence of direct-current field, with effective energy barriers of 4.6 and 44.4 K, respectively. The enhancement of the effective energy barrier of the latter can be attributed to the presence of a large energy gap between the ground and first excited Kramers doublets, triggered by the change in coordination environments around the lanthanide centers.

Observation of Slow Relaxation and Single-Molecule Toroidal Behavior in a Family of Butterfly-Shaped Ln4 Complexes.

A family of five isostructural butterfly complexes with a tetranuclear [Ln4 ] core of the general formula [Ln4 (LH)2 (µ2 -η1 η1 Piv)(η2 -Piv)(µ3 -OH)2 ]⋅x H2 O⋅y MeOH⋅z CHCl3 (1: Ln=DyIII , x=2, y=2, z=0; 2: Ln=TbIII , x=0, y=0, z=6; 3: Ln=ErIII , x=2, y=2, z=0; 4: Ln=HoIII , x=2, y=2, z=0; 5: Ln=YbIII , x=2, y=2, z=0; LH4 =6-{[bis(2-hydroxyethyl)amino]methyl}-N'-(2-hydroxy-3-methoxybenzylidene)picolinohydrazide; PivH=pivalic acid) was isolated and characterized both structurally and magnetically. Complexes 1-5 were probed by direct and alternating current (dc and ac) magnetic susceptibility measurements and, except for 1, they did not display single-molecule magnetism (SMM) behavior. The ac magnetic susceptibility measurements show frequency-dependent out-of-phase signals with one relaxation process for complex 1 and the estimated effective energy barrier for the relaxation process was found to be 49 K. We have carried out extensive ab initio (CASSCF+RASSI-SO+SINGLE_ANISO+POLY_ANISO) calculations on all the five complexes to gain deeper insights into the nature of magnetic anisotropy and the presence and absence of slow relaxation in these complexes. Our calculations yield three different exchange coupling for these Ln4 complexes and all the extracted J values are found to be weakly ferro/antiferromagentic in nature (J1 =+2.35, J2 =-0.58, and J3 =-0.29 cm-1 for 1; J1 =+0.45, J2 =-0.68, and J3 =-0.29 cm-1 for 2; J1 =+0.03, J2 =-0.98, and J3 =-0.19 cm-1 for 3; J1 =+4.15, J2 =-0.23, and J3 =-0.54 cm-1 for 4 and J1 =+0.15, J2 =-0.28, and J3 =-1.18 cm-1 for 5). Our calculations reveal the presence of very large mixed toroidal moment in complex 1 and this is essentially due to the specific exchange topology present in this cluster. Our calculations also suggest presence of single-molecule toroics (SMTs) in complex 2. For complexes 3-5 on the other hand, the transverse anisotropy was computed to be large, leading to the absence of slow relaxation of magnetization. As the magnetic field produced by SMTs decays faster than the normal spin moments, the concept of SMTs can be exploited to build qubits in which less interference and dense packing are possible. Our systematic study on these series of Ln4 complexes suggest how the ligand design can help to bring forth such SMT characteristics in lanthanide complexes.