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Imidazo[1,5-a]pyridine-based derivatives as highly fluorescent dyes
No full textThis minireview collects the results that we obtained in the recent years on luminescent compounds based on imidazo[1,5-a]pyridines, an interesting class of heterocycles characterized by relevant photophysical properties like high Stokes shift, good absolute quantum yields, good photostability and a λem modulable depending on the substituents on the heterocyclic ring.
These peculiar features can be transferred to the corresponding complexes when imidazo[1,5-a]pyridines are used as ligands. Herein we report on the photoluminescent behavior of zinc(II) and silver(I) complexes with 1-pyridylimidazo[1,5-a]pyridines acting as N,N-bidentate, neutral ligands. Then, zinc(II) and boron(III) compounds bearing N,O- monoanionic 2-(imidazo[1,5-a]pyridin-3-yl)phenolates will also be described. In all cases, a bright fluorescence emission was observed, either in the solid state or in solution; some promising derivatives showed a relevant photoluminescent behavior also when analyzed as thin films.
A full spectroscopic characterization, combined with a theoretical approach (DFT), allowed to establish structure-properties relationships for the species investigated
Long-Alkyl Chain Functionalized Imidazo[1,5-a]pyridine Derivatives as Blue Emissive Dyes
Full text linkA series of boron difluoride compounds with 2-(imidazo[1,5-a]pyridin-3-yl)phenols bearing alkylic chains at the 1-position has been synthesized and characterized both with 1H and 13C NMR and infrared spectroscopy. This series of compounds displayed blue emission in solution and in thin polymeric films, with interesting features like large Stokes shifts and good fluorescence quantum yields. Time-Dependent Density Functional Theory (TD-DFT) calculations allowed for the identification of the main electronic transitions as intra ligand transitions (1ILT), as corroborated by the Natural Transition Orbitals (NTOs) shapes
Tuning the Fluorescence Emission and HOMO-LUMO Band Gap in Homoleptic Zinc(II) Complexes with N,O-Bidentate (Imidazo[1,5-a]pyrid-3-yl)phenols
No full textA series of homoleptic zinc(II) complexes of the general formula [Zn(L R ) 2 ] (HL R : (imidazo[1,5-a]pyrid-3-yl)phenol; R: para-substituent to the phenol) have been synthesized. The single-crystal X-ray structure analysis of complex [Zn(L H ) 2 ] (1) confirmed the expected N,O-bidentate coordination of L R , via the pyridine-like nitrogen of the imidazo[1,5-a]pyridine skeleton and the phenolate oxygen. The photophysical properties of the complexes have been investigated in dichloromethane solution, showing fluorescence emission when excited with UV light (λ exc = 340–360 nm). The intensity and λ max of the emission are both significantly influenced by the R-substituent, the emission maxima moving from blue (R = CF 3 , Zn(L CF3 ) 2 ] (6)) to orange (R = NO 2 , Zn(L NO2 ) 2 ] (7). Most of [Zn(L R ) 2 ] compounds are characterized by moderate-to-good absolute photoluminescence quantum yields, with a maximum of 0.33 for [Zn(L H ) 2 ] (1). Density functional calculations allowed to identify the Natural Transition Orbitals involved in the electronic transitions and define the main transition as being HOMO-LUMO (>95 %) in character. A good linear correlation was found between the HOMO energy and the Hammett σ p constants associated to the R-substituent, whereas the fluorescence behavior has been described in terms of HOMO-LUMO band gap
Boron-Centered Compounds: Exploring the Optical Properties of Spiro Derivatives with Imidazo[1,5-a]Pyridines
Full text linkFive boron-centered spiro compounds with imidazo[1,5-a]pyridin-3-yl phenols as ligands were synthesized and thoroughly characterized through 1H-NMR, 13C-NMR, infrared spectroscopy, and X-ray single crystal analysis. The fluorescence properties of these compounds in solution and in the solid state were investigated, revealing blue emission with wavelengths maxima dependent on the electronic properties of the substituents on the ligands in solution, and an orange-red emission in the solid state. Time-Dependent Density Functional Theory (TD-DFT) calculations were performed to describe the nature of the transition
Gizmo: The Theatre of Automation in the post-labour society of Hammerfest
No full textWhile technological development and the rising Second Machine Age are already firmly affecting the notion of labour and the consequent disposition of our cities and territories, the remote island of Hammerfest, in the Arctic regions of Finnmark, prefigures the conditions for a radical rebirth. The full extents of automation, resulting in a post-labour organisation of economy, envisions the return of the homo ludens and enhances play as fundamental base of the new society. The explosive decentralisation of production and distribution suddenly wipes out the city, the core centre of our consumerist lives, and promotes the return to the landscape, where new pillars of society are established. On this island of utopian playground, individuals are now fully capable of engendering the shape of their existence, clustering around the ludic elements and interacting with each other in playful activities, while machines take care of their fundamental needs. Among the elements, the Theatre represents the highest form of play and, therefore, the most essential component of public life. Facing the growing automated port and the perished city, the machine of the theatre is a bridge between land and sea, on the particular conditions of a site that constantly changes under the cyclical variations of the tide. In front of the spectacle of automation, what humans stare at is the activity that has been taken away from them, the agency of their actions. A new kind of theatricality is therefore needed. Since the demise of labour invests anyone with the possibility of becoming actors of the play, the sense of spectatorship itself is questioned. Far from the optical relation of the theatron (sight), that has so far embodied its cornerstone, the theatre has now to be subjected to another relation, suggested by the word drama (action), thus endowing the becoming performative of production. The Theatre of Automation is therefore a social endeavour, aiming at bringing the theatrical performance to the level of a collective form of life, where the role of the spectator merges with the one of the actor. In other terms, the machine of the theatre takes active part in the transformation of the site, unfolding and accelerating the artificial manipulation of the territory at the hand of technology. As an act of formation, first, of physical, cultural and ultimately of political nature, the Theatre measures the pace of changes, interpolating the urgency of human artifex with the rhythm of natural systems. When climate change and sea level rise will set the eventual limit of the Machine, interrupting its floating dance on the tides, the Theatre will come to its final act. Rich with the collective memory of the site, it will close its stage and set sail towards new destinations, bearing the paradigm of a new society, on the threshold between human, machine and nature.Architecture, Urbanism and Building Sciences | Transitional Territorie
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
H-bonding dependent phosphorescence in a mixed ligand copper(I) complex
No full textThe mixed ligand copper(I) derivative [Cu(PPh3)2(j2-O,O00-lact)] (1) (lact = L-(+)-lactate) has been prepared
and fully characterized. NMR studies indicated the occurrence of a fluxional behavior involving
the lactate anion, in solution. The a-hydroxycarboxylate ligand is responsible for the generation of a catemeric
O–H O(CO) H-bonding network that strongly influences the photophysical properties of 1, in the
solid state. Indeed, when irradiated with UV light the title compound shows a bright phosphorescence,
which as suggested by DFT calculations is strictly related to the abovementioned H-bonding network
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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