Comparing the structures and photophysical properties of two charge transfer co-crystals.

Organic co-crystals have emerged as a promising class of semiconductors for next-generation optoelectronic devices due to their unique photophysical properties. This paper presents a joint experimental-theoretical study comparing the crystal structure, spectroscopy, and electronic structure of two charge transfer co-crystals. Reported herein is a novel co-crystal Npe:TCNQ, formed from 4-(1-naphthylvinyl)pyridine (Npe) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) via molecular self-assembly. This work also presents a revised study of the co-crystal composed of Npe and 1,2,4,5-tetracyanobenzene (TCNB) molecules, Npe:TCNB, herein reported with a higher-symmetry (monoclinic) crystal structure than previously published. Npe:TCNB and Npe:TCNQ dimer clusters are used as theoretical model systems for the co-crystals; the geometries of the dimers are compared to geometries of the extended solids, which are computed with periodic boundary conditions density functional theory. UV-Vis absorption spectra of the dimers are computed with time-dependent density functional theory and compared to experimental UV-Vis diffuse reflectance spectra. Both Npe:TCNB and Npe:TCNQ are found to exhibit neutral character in the S0 state and ionic character in the S1 state. The high degree of charge transfer in the S1 state of both Npe:TCNB and Npe:TCNQ is rationalized by analyzing the changes in orbital localization associated with the S1 transitions.

Evaluating Web-Based Care for Mental Health and Substance Use Issues for Lesbian, Gay, Bisexual, Transgender, Queer, Questioning, and 2-Spirit Youths in the Context of the COVID-19 Pandemic: Community-Based Participatory Research Study.

BACKGROUND: Mental health (MH) and substance use (SU) care supports are often difficult to access for the lesbian, gay, bisexual, transgender, queer, questioning, and 2-spirit (LGBTQ2S+) population. There is little known on how the shift to web-based care has affected and changed the experiences of LGBTQ2S+ youths within the MH care system. OBJECTIVE: This study sought to examine how web-based care modalities have affected access to care and quality of care for LGBTQ2S+ youths seeking MH and SU services. METHODS: Researchers used a web-based co-design method to explore this population's relationship with MH and SU care supports, focusing on the experiences of 33 LGBTQ2S+ youths and their relationship with MH and SU supports during the COVID-19 pandemic. A participatory design research method was used to gain experiential knowledge of LGBTQ2S+ youths' lived experience with accessing MH and SU care. Thematic analysis was used to examine the resulting audio-recorded data transcripts and create themes. RESULTS: Themes related to web-based care included accessibility, web-based communication, provision of choice, and provider relationship and interactions. Barriers to care were identified in particular for disabled youths, rural youths, and other participants with marginalized intersecting identities. Unexpected benefits of web-based care were also found and emphasize the idea that this modality is beneficial for some LGBTQ2S+ youths. CONCLUSIONS: During the COVID-19 pandemic, a time where MH- and SU-related problems have increased, programs need to reevaluate current measures so that the negative effects of web-based care modalities can be reduced for this population. Implications for practice encourage service providers to be more empathetic and transparent when providing services for LGBTQ2S+ youths. It is suggested that LGBTQ2S+ care should be provided by LGBTQ2S+ folks or organizations or service providers who are trained by LGBTQ2S+ community members. Additionally, hybrid models of care should be established in the future so that LGBTQ2S+ youths have the option to access in-person services, web-based ones, or both as there can be benefits to web-based care once it has been properly developed. Implications for policy also include moving away from a traditional health care team model and developing free and lower-cost services in remote areas.

A population-based approach to integrated healthcare delivery: a scoping review of clinical care and public health collaboration.

BACKGROUND: A population-based approach to healthcare goes beyond the traditional biomedical model and addresses the importance of cross-sectoral collaboration in promoting health of communities. By establishing partnerships across primary care (PC) and public health (PH) sectors in particular, healthcare organizations can address local health needs of populations and improve health outcomes. The purpose of this study was to map a series of interventions from the empirical literature that facilitate PC-PH collaboration and develop a resource for healthcare organizations to self-evaluate their clinical practices and identify opportunities for collaboration with PH. METHODS: A scoping review was designed and studies from relevant peer-reviewed literature and reports between 1990 and 2017 were included if they met the following criteria: empirical study methodology (quantitative, qualitative, or mixed methods), based in US, Canada, Western Europe, Australia or New Zealand, describing an intervention involving PC-PH collaboration, and reporting on structures, processes, outcomes or markers of a PC-PH collaboration intervention. RESULTS: Out of 2962 reviewed articles, 45 studies with interventions leading to collaboration were classified into the following four synergy groups developed by Lasker's Committee on Medicine and Public Health: Coordinating healthcare services (n = 13); Applying a population perspective to clinical practice (n = 21); Identifying and addressing community health problems (n = 19), and Strengthening health promotion and health protection (n = 21). Furthermore, select empirical examples of interventions and their key features were highlighted to illustrate various approaches to implementing collaboration interventions in the field. CONCLUSIONS: The findings of our review can be utilized by a range of organizations in healthcare settings across the included countries. Furthermore, we developed a self-evaluation tool that can serve as a resource for clinical practices to identify opportunities for cross-sectoral collaboration and develop a range of interventions to address unmet health needs in communities; however, the generalizability of the findings depends on the evaluations conducted in individual studies in our review. From a health equity perspective, our findings also highlight interventions from the empirical literature that address inequities in care by targeting underserved, high-risk populations groups. Further research is needed to develop outcome measures for successful collaboration and determine which interventions are sustainable in the long term.

Taking Advantage of Disorder: Small-Molecule Organic Glasses for Radiation Detection and Particle Discrimination.

A series of fluorescent silyl-fluorene molecules were synthesized and studied with respect to their photophysical properties and response toward ionizing neutron and gamma-ray radiation. Optically transparent and stable organic glasses were prepared from these materials using a bulk melt-casting procedure. The prepared organic glass monoliths provided fluorescence quantum yields and radiation detection properties exceeding the highest-performing benchmark materials such as solution-grown trans-stilbene crystals. Co-melts based on blends of two different glass-forming compounds were prepared with the goal of enhancing the stability of the amorphous state. Accelerated aging experiments on co-melt mixtures ranging from 0% to 100% of each component indicated improved resistance to recrystallization in the glass blends, able to remain fully amorphous for >1 month at 60 °C. Secondary dopants comprising singlet fluorophores or iridium organometallic compounds provided further improved detection efficiency, as evaluated by light yield and neutron/gamma particle discrimination measurements. Optimized singlet and triplet doping levels were determined to be 0.05 wt % 1,4-bis(2-methylstyryl)benzene singlet fluorophore and 0.28 wt % Ir3+, respectively.

Factors associated with transition to a nursing home in older adults living in naturally occurring retirement communities.

BACKGROUND: Naturally occurring retirement communities (NORCs) are geographic areas (generally high-rise buildings or neighborhoods) that have a high concentration of individuals 65 years and older. Supportive service programs in NORCs can address resident needs and delay nursing home (NH) admission but understanding what factors are associated with NORC residents requiring NH admission is needed to tailor such programs. Our aim was to examine individual- and neighborhood-level factors associated with NH wait-list status in NORC residents in Ontario. METHODS: We conducted a population-based, cross-sectional study of Ontario adults 65 years of age or older living in a NORC building as of January 1, 2020, by linking a provincial registry of NORC high-rise buildings with health administrative data. Older adults were classified as being on the NH wait-list if they had an open application for a NH on the index date. We conducted a multilevel logistic regression analysis using generalized estimating equations to determine individual- and neighborhood-level factors associated with NH wait-list status, including sociodemographic, clinical, healthcare use, and building factors. We explored the role of sex and age through stratification by sex (male, female) and age (65-80 and 80+ years). RESULTS: Among 220,864 NORC residents, 4710 individuals (2.1%) were on the NH wait-list. Female sex, older age, immigrant status, dementia diagnosis, receiving homecare, multimorbidity, and polypharmacy (five or more unique drug names) were associated with an increased odds of wait-list status. Several neighborhood-level variables were associated with a significantly increased likelihood of wait-list status, including low income, high dependency, high ethnic diversity, and living in a building with supports. CONCLUSION: NORC supportive service programs can be tailored to account for the factors associated with NH wait-list status, allowing NORC residents who are living in the community to age in their desired place and achieve optimal health outcomes.

Development of the Preferred Components for Co-Design in Research Guideline and Checklist: Protocol for a Scoping Review and a Modified Delphi Process.

BACKGROUND: There is increasing evidence that co-design can lead to more engaging, acceptable, relevant, feasible, and even effective interventions. However, no guidance is provided on the specific designs and associated methods or methodologies involved in the process. We propose the development of the Preferred Components for Co-design in Research (PRECISE) guideline to enhance the consistency, transparency, and quality of reporting co-design studies used to develop complex health interventions. OBJECTIVE: The aim is to develop the first iteration of the PRECISE guideline. The purpose of the PRECISE guideline is to improve the consistency, transparency, and quality of reporting on studies that use co-design to develop complex health interventions. METHODS: The aim will be achieved by addressing the following objectives: to review and synthesize the literature on the models, theories, and frameworks used in the co-design of complex health interventions to identify their common elements (components, values or principles, associated methods and methodologies, and outcomes); and by using the results of the scoping review, prioritize the co-design components, values or principles, associated methods and methodologies, and outcomes to be included in the PRECISE guideline. RESULTS: The project has been funded by the Canadian Institutes of Health Research. CONCLUSIONS: The collective results of this project will lead to a ready-to-implement PRECISE guideline that outlines a minimum set of items to include when reporting the co-design of complex health interventions. The PRECISE guideline will improve the consistency, transparency, and quality of reports of studies. Additionally, it will include guidance on how to enact or enable the values or principles of co-design for meaningful and collaborative solutions (interventions). PRECISE might also be used by peer reviewers and editors to improve the review of manuscripts involving co-design. Ultimately, the PRECISE guideline will facilitate more efficient use of new results about complex health intervention development and bring better returns on research investments. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): PRR1-10.2196/50463.

Ontario's COVID-19 Modelling Consensus Table: mobilizing scientific expertise to support pandemic response.

SETTING: COVID-19 has highlighted the need for credible epidemiological models to inform pandemic policy. Traditional mechanisms of commissioning research are ill-suited to guide policy during a rapidly evolving pandemic. At the same time, contracting with a single centre of expertise has been criticized for failing to reflect challenges inherent in specific modelling approaches. INTERVENTION: This report describes an alternative approach to mobilizing scientific expertise. Ontario's COVID-19 Modelling Consensus Table (MCT) was created in March 2020 to enable rapid communication of credible estimates of the impact of COVID-19 and to accelerate learning on how the disease is spreading and what could slow its transmission. The MCT is a partnership between the province and academic modellers and consists of multiple groups of experts, health system leaders, and senior decision-makers. Armed with Ministry of Health data, the MCT meets once per week to share results from modelling exercises, generate consensus judgements of the likely future impact of COVID-19, and discuss decision-makers' priorities. OUTCOMES: The MCT has enabled swift access to data for participants, a structure for developing consensus estimates and communicating these to decision-makers, credible models to inform health system planning, and increased transparency in public reporting of COVID-19 data. It has also facilitated the rapid publication of research findings and its incorporation into government policy. IMPLICATIONS: The MCT approach is one way to quickly draw on scientific advice outside of government and public health agencies. Beyond speed, this approach allows for nimbleness as experts from different organizations can be added as needed. It also shows how universities and research institutes have a role to play in crisis situations, and how this expertise can be marshalled to inform policy while respecting academic freedom and confidentiality.

RéSUMé: LIEU: La COVID-19 a mis en évidence le besoin de modèles épidémiologiques crédibles pour éclairer la politique pandémique. Les mécanismes habituels pour commander des travaux de recherche sont peu propices à orienter les politiques lors d'une pandémie qui évolue rapidement. En même temps, la passation de contrats avec un seul centre d'expertise est critiquée, car elle ne tient pas compte des difficultés inhérentes de certaines approches de modélisation. INTERVENTION: Le présent rapport décrit une approche de rechange pour mobiliser le savoir scientifique. L'Ontario a créé en mars 2020 une Table de concertation sur la modélisation (TCM) qui permet de communiquer de façon rapide et fiable les estimations des effets de la COVID-19 et d'apprendre plus vite comment la maladie se propage et ce qui pourrait en ralentir la transmission. La TCM, un partenariat entre les modélisateurs de la province et des milieux universitaires, est composée de plusieurs groupes d'experts, de dirigeants du système de santé et de décideurs de haut niveau. Armée des données du ministère de la Santé, la TCM se réunit une fois par semaine pour partager les résultats d'exercices de modélisation, générer des jugements consensuels sur les futurs effets probables de la COVID-19 et discuter des priorités des décideurs. RéSULTATS: La TCM rend possible un accès rapide aux données pour les participants, une structure pour élaborer des estimations consensuelles et les communiquer aux décideurs, des modèles fiables pour éclairer la planification du système de santé, ainsi qu'une transparence accrue dans la communication des données sur la COVID-19 au public. Elle facilite aussi la publication rapide des résultats de recherche et leur intégration dans la politique gouvernementale. CONSéQUENCES: L'approche de la TCM est un moyen d'obtenir rapidement des conseils scientifiques à l'extérieur du gouvernement et des organismes de santé publique. Au-delà de sa rapidité, cette approche offre une grande souplesse, car des experts de différents organismes peuvent être ajoutés au besoin. Elle montre aussi que les universités et les établissements de recherche ont un rôle à jouer dans les situations de crise, et qu'il est possible de mobiliser leurs compétences pour éclairer les politiques tout en respectant la liberté et la confidentialité des milieux de la recherche et de l'enseignement.

Is vaping cessation like smoking cessation? A qualitative study exploring the responses of youth and young adults who vape e-cigarettes.

INTRODUCTION: Young people are now seeking help to quit vaping. However, little is known about vaping cessation. To bridge the gap between the current state of research and the urgent need for interventions, practitioners have drawn upon smoking cessation models under the assumption that vaping and smoking are fairly similar. In this study, we sought to understand the nature and extent to which vaping is similar to smoking in order to inform the development of vaping cessation interventions for young people. METHODS: Seven focus groups were conducted between November 2019 and February 2020 among youth (ages 16-18) and young adults (ages 19-29) living in the Greater Toronto Area who self-identified as e-cigarette vapers and expressed interest in vaping cessation (n = 41). Focus groups were audio recorded, transcribed verbatim, and analyzed using thematic analysis methods. RESULTS: Perceived similarities between vaping and smoking emerged from participant narratives: three themes relating to barriers to quitting (social benefits, stress reduction, sensory and behavioural gratification), and three relating to reasons for quitting (financial loss, industry influence, dependence). However, there were also perceived differences that emerged: three themes relating to barriers to quitting vaping (enjoyment of flavours, convenience and discreetness, lack of self-awareness of vaping behaviours), and two relating to reasons for quitting vaping (lack of trusted information, perceived social acceptability). CONCLUSIONS: Although there is significant overlap between vaping and smoking, understanding perceived differences in barriers to quitting and reasons for quitting is critical to advancing vaping cessation research and practice among young people.

Visually estimated coronary artery calcium score improves SPECT-MPI risk stratification.

AIMS: Computed tomographic attenuation correction (CTAC) scans for single photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) may reveal coronary artery calcification. The independent prognostic value of a visually estimated coronary artery calcium score (VECACS) from these low-dose, non-gated scans is not established. METHODS & RESULTS: VECACS was evaluated in 4,720 patients undergoing SPECT-MPI with CTAC using a 4-point scale. Major adverse cardiac events (MACE) were defined as all-cause mortality, acute coronary syndrome, or revascularization > 90 days after SPECT-MPI. Independent associations with MACE were determined with multivariable Cox proportional hazards analyses adjusted for age, sex, past medical history, perfusion findings, and left ventricular ejection fraction. During a median follow up of 2.9 years (interquartile range 1.8 - 4.2), 494 (10.5%) patients experienced MACE. Compared to absent VECACS, patients with increased VECACS were more likely to experience MACE (all log-rank p < 0.001), and findings were similar when stratified by normal or abnormal perfusion. Multivariable analysis showed an increased MACE risk associated with VECACS categories of equivocal (adjusted hazard ratio [HR] 2.54, 95% CI 1.45-4.45, p = 0.001), present (adjusted HR 2.44, 95% CI 1.74-3.42, p < 0.001) and extensive (adjusted HR 3.47, 95% CI 2.41-5.00, p < 0.001) compared to absent. Addition of VECACS to the multivariable model improved risk classification (continuous net reclassification index 0.207, 95% CI 0.131 - 0.310). CONCLUSION: VECACS was an independent predictor of MACE in this large SPECT-MPI patient cohort. VECACS from CTAC can be used to improve risk stratification with SPECT-MPI without additional radiation.

Assessing the purity of metal-organic frameworks using photoluminescence: MOF-5, ZnO quantum dots, and framework decomposition.

Photoluminescence (PL) spectroscopy was used to characterize nanoscale ZnO impurities, amine-donor charge-transfer exciplexes, and framework decomposition in samples of MOF-5 prepared by various methods. The combined results cast doubt on previous reports describing MOF-5 as a semiconductor and demonstrate that PL as a tool for characterizing MOF purity possesses advantages such as simplicity, speed, and sensitivity over currently employed powder XRD MOF characterization methods.

Isostructural single-chain and single-molecule magnets.

Isostructural single-chain magnet (SCM) and single-molecule magnets (SMM) with formulas [Mn(6)X(2)(salox)(6)O(2)(N(3))(8)] (X = Mn(II) (1), Cd(II) (2); H(2)salox = salicylaldoxime) have been synthesized and magnetically characterized. Complexes 1 and 2 possess significantly different magnetization reversal barriers of U(eff) = 100.3 and 57.0 K, in spite of comparable uniaxial anisotropies (D) and ground state spin values (S). These observations are indicative of the intrinsic spin dynamics in these structurally related yet magnetically distinct SCM/SMM systems.

Large spin-state changes in isostructural cyanate- and azide-bridged Mn(3)(III)Mn(2)(II) single-molecule magnets.

We prepared three structurally related Mn(3)(III)Mn(2)(II) complexes that possess S approximately 1-11 spin ground states as a result of variations in the geometry and identity of mu(2)-eta(1):eta(1) bridging groups. These complexes function as single-molecule magnets yet demonstrate other interesting behavior such as quasi-classical magnetization hysteresis and comparable magnetization reversal barriers (U(eff)).

Towards Value in an Integrated Care Environment: Early Lessons from an Ontario Health Team.

Integrated healthcare models are being experimented with in many jurisdictions as a way to improve patient care and lower system costs. This commentary presents early lessons from one Ontario Health Team as it works towards new models of care. The authors recount early discussions on developing an integrated health services network, how funding for "winter surge initiatives" became an opportunity to test ideas and how these experiences are informing current planning. Some of the early lessons learned include the value of trusted relationships, moving care upstream and framing problems as collective challenges.

Nanomodulation of molecular nanomagnets.

Detailed synthetic, structural, and magnetic characterizations for a family of six [Mn(3)Zn(2)](13+) complexes are presented. These complexes have planar [Mn(3)(III)-(mu(3)-oxo)](7+) core magnetic units and have formulas represented by [cation](3)[Mn(3)Zn(2)(R-salox)(3)O(N(3))(6)X(2)], where [cation](+) = [NEt(4)](3)(+) or [AsPh(4)](3)(+); R = H or Me; and X = Cl(-), Br(-), I(-), or N(3)(-). Least-squares fits to the magnetic susceptibility data for these complexes indicate large negative values of the axial zero field splitting (ZFS) parameter D (approximately -1.1 K) and spin ground states ranging from a highly spin-mixed S approximately 1 to a reasonably isolated S = 6 (DeltaE(S = 5) = 69.2 K). The strength and magnitude of the intramolecular exchange interactions have been observed to change with the crystal packing as a result of systematic variations in the co-crystallizing cation, terminal ion, and oximate ligand. Alternating current susceptibility data were collected from 1.8-7 K at 10-997 Hz, revealing strong frequency-dependent peaks in the out-of-phase susceptibility (chi''(M)) for ferromagnetic S = 6 complexes 1, 2, and 6. Fitting of these data to the Arrhenius equation gave U(eff) = 44.0 K and tau(0) = 3.8 x 10(-8) s for [NEt(4)](3)[Mn(3)Zn(2)(salox)(3)O(N(3))(6)Cl(2)] (1), and U(eff) = 45.6 K and tau(0) = 2.1 x 10(-7) s for [NEt(4)](3)[Mn(3)Zn(2)(Me-salox)(3)O(N(3))(6)Cl(2)] (6). The enhanced relaxation behavior in complex 6 is associated with stronger ferromagnetic exchange interactions and a more isolated S = 6 ground state than in 1 and 2. Comprehensive high-frequency electron paramagnetic resonance (HFEPR) experiments were conducted on single crystals of complexes 1, 2, and 6, revealing sharp absorption peaks and allowing for the precise determination of ZFS parameters. Similar experiments on [AsPh(4)](3)[Mn(3)Zn(2)(salox)(3)O(N(3))(6)Cl(2)] (4) resulted in the observation of a broad absorption peak, consistent with the highly spin-mixed ground state. Single crystal magnetization hysteresis measurements on complexes 1 and 2 indicate SMM behavior via temperature- and sweep-rate dependent hysteresis loops and the observance of very sharp quantum tunneling resonances. Additionally, the Hamiltonian parameters derived from the magnetic data, HFEPR, and hysteresis measurements are in good agreement and highlight the relationships between superexchange, spin-orbit interactions, and the varied relaxation behavior in these complexes.

Charge-separation in uranium diazomethane complexes leading to C-H activation and chemical transformation.

The reaction of diphenyldiazomethane with [((t-BuArO)3tacn)UIII] (1) results in an eta(2)-bound diphenyldiazomethane uranium complex. This complex exhibits unusual electronic properties as a charge-separated species with a radical anionic open-shell ligand, [((t-BuArO)3tacn)UIV(eta2-NNCPh2)] (2). Treating Ph2CN2 with a uranium complex that contains a sterically more demanding adamantane functionalized ligand, [((AdArO)3tacn)UIII] (3) results in an unprecedented C-H activation and nitrogen insertion to produce a five-membered heterocyclic indazole complex, [((AdArO)3tacn)UIV(eta(2)-3-phen(Ind))] (5). X-ray crystallography and spectroscopic characterization of these two compounds show that the [((t-BuArO)3tacn)UIV(eta(2)-NNCPh2)] compound is a U(IV) complex with a radical anionic ligand, whereas [((AdArO)3tacn)UIV(eta(2)-3-phen(Ind))] is a U(IV) f (2) species with a closed-shell ligand.

Single-molecule-magnet behavior and spin changes affected by crystal packing effects.

Five Mn 3Zn 2 heterometallic complexes have been synthesized and structurally and magnetically characterized. Spin ground states up to S = 6 have been observed for these complexes and are shown to depend on the cocrystallizing cation and on the terminal ligand. Large axial zero-field interactions ( D = -1.16 K) are the result of near-parallel alignment of the Mn (III) Jahn-Teller axes. High-frequency electron paramagnetic resonance, single-crystal magnetization hysteresis, and alternating current susceptibility measurements are presented to characterize [NEt 4] 3[Mn 3Zn 2(salox) 3O(N 3) 6X 2] [X (-) = Cl (-) ( 1), Br (-) ( 2)] and [AsPh 4] 3[Mn 3Zn 2(salox) 3O(N 3) 6Cl 2] ( 3) and reveal that 1 and 2 are single-molecule magnets ( U eff = 44 K), while 3 is not.

Versatile Synthesis and Fluorescent Labeling of ZIF-90 Nanoparticles for Biomedical Applications.

We describe a versatile method for the synthesis and fluorescent labeling of ZIF-90 nanoparticles (NPs). Gram-scale quantities of NPs can be produced under mild conditions, circumventing the need for high temperatures and extended reaction periods required by existing procedures. Monitoring the reaction in situ using UV-vis spectroscopy reveals that ZIF-90 NP nucleation in solution starts within seconds. In addition to reporting a method to reproducibly form sub-100 nm ZIF-90 particles, we show that particles of various sizes can be produced, ranging from 30 to 1000 nm, by altering amine chemistry or reaction temperature. The presence of linker aldehyde groups on the NP surface allows for postsynthetic labeling with amine-functionalized fluorescent dyes, providing utility for imaging within biological systems. In vitro cell studies show that ZIF-90 NPs have a high rate of cellular internalization, provide finite degradation periods of the order of several weeks, and are biocompatible with six different cell lines (>90% viable when incubated with NPs for up to 7 days). These features highlight the potential for use of ZIF-90 nanostructures in bioimaging and targeted drug delivery applications.

Guest-Induced Emergent Properties in Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) are crystalline nanoporous materials comprised of organic electron donors linked to metal ions by strong coordination bonds. Applications such as gas storage and separations are currently receiving considerable attention, but if the unique properties of MOFs could be extended to electronics, magnetics, and photonics, the impact on material science would greatly increase. Recently, we obtained "emergent properties," such as electronic conductivity and energy transfer, by infiltrating MOF pores with "guest" molecules that interact with the framework electronic structure. In this Perspective, we define a path to emergent properties based on the Guest@MOF concept, using zinc-carboxylate and copper-paddlewheel MOFs for illustration. Energy transfer and light harvesting are discussed for zinc carboxylate frameworks infiltrated with triplet-scavenging organometallic compounds and thiophene- and fullerene-infiltrated MOF-177. In addition, we discuss the mechanism of charge transport in TCNQ-infiltrated HKUST-1, the first MOF with electrical conductivity approaching conducting organic polymers. These examples show that guest molecules in MOF pores should be considered not merely as impurities or analytes to be sensed but also as an important aspect of rational design.

Charge-transfer guest interactions in luminescent MOFs: implications for solid-state temperature and environmental sensing.

One of the ongoing goals in the field of porous materials is the design and synthesis of materials that possess chemical structures amenable for use in sensing applications. We describe the preparation, luminescence characteristics, and environmental sensing properties of variants of the aluminum-based MOF [Al(OH)(O(2)C-C(10)H(6)-CO(2))](∞). Careful activation of the open framework complex, 1, yielded a dynamic structural transformation to a non-porous form, 2, that exhibited strong inter-linker interactions and red-shifted emission characteristics indicative of dimer formation. We also demonstrate the formation of highly luminescent ground-state charge-transfer (CT) complexes between 1 and the electron-donating amines dimethylamine (DMA) (1a), and N,N-diethylaniline (DEA) (1b), both of which exhibit dual-emission characteristics and a ratiometric luminescence response that is sensitive to temperature and solvent polarity. Steady-state and time-resolved measurements on 1a, 1b, and 2 indicate that the MOF structures stabilize ground-state CT interactions that are distinct from the weakly-bound exciplexes formed in comparable mixtures of purely organic components. The spectra for 1a and 1b also indicate different temperature dependencies that correspond to thermally-activated complex formation (ΔH(f) = +1.1 ± 0.2 kcal mol(-1)) in 1a and static quenching effects (ΔH(f) = -2.2 ± 0.3 kcal mol(-1)) in 1b. The addition of ethanol, isopropanol, toluene, or chloroform to suspensions of 1b indicate destabilization of the CT state with increasing solvent polarity, which suggests the generalized application of this or related materials in sensor applications.