0000000001309642
AUTHOR
J. Sérgio Seixas De Melo
showing 13 related works from this author
Polyamine Linear Chains Bearing Two Identical Terminal Aromatic Units. Evidence for a Photo Induced Bending Movement
2001
Abstract Several chemosensors bearing a fluorescent unit at both ends of a linear polyamine chain were synthesised. The protonation as well as the association constants with Cu2+ and Zn2+ were determined by potentiometry in 0.15 mol dm−3 NaCl at 298.1 K. In the case of 1,16-bis(1-naphthylmethyl)-1,4,7,10,13,16-hexaazadecane hexahydrochloride (L1), formation of an excimer emission in aqueous acidic solutions was observed. The system was characterized by steady state fluorescence emission and by time resolved fluorescence. In the ground state the molecule is expected to adopt a more or less linear conformation, while in the excited state a bending movement of the chain must occur in order to …
Switching from intramolecular energy transfer to intramolecular electron transfer by the action of pH and Zn2+ co-ordination
2002
Abstract Intramolecular electron (eT) and energy transfer (ET) have shown to occur in a covalently linked donor–acceptor (CLDA) system consisting of a naphthalene donor covalently linked through a polyamine chain connector to an anthracene acceptor; the connector has been chosen in order to switch ON or OFF the energy flux as a function of its protonation state as well as by co-ordination to Zn 2+ . The largest energy transfer efficiency ( η =0.61) occurs for the fully protonated form (pH 9 (eT) from the lone pairs of the nitrogens to the excited fluorophore takes place, leading to complete quenching of the emission. On the other hand at neutral and basic pH values, co-ordination of Zn 2+ p…
Energetics and Dynamics of Naphthalene Polyaminic Derivatives. Influence of Structural Design in the Balance Static vs Dynamic Excimer Formation
2003
Two new fluorescent macrocyclic structures bearing two naphthalene (Np) units at both ends of a cyclic polyaminic chain were investigated with potentiometric, fluorescence (steady-state and time-resolved) and laser flash photolysis techniques. The fluorescence emission studies show the presence of an excimer species whose formation depends on the protonation state of the polyamine chains implying the existence of a bending movement (occurring in both the ground and in the first singlet excited state), which allows the two naphthalene units to approach and interact. For comparison purposes, one bis-chromophoric compound containing a rigid chain (piperazine unit) was also investigated. Its em…
Room-Temperature Phosphorescence and Efficient Singlet Oxygen Production by Cyclometalated Pt(II) Complexes with Aromatic Alkynyl Ligands
2020
The synthesis of five novel cyclometalated platinum(II) compounds containing five different alkynyl-chromophores was achieved by the reaction of the previously synthesized Pt–Cl cyclometalated compound (1) with the corresponding RC≡CH by a Sonogashira reaction. It was observed that the spectral and photophysical characteristics of the cyclometalated platinum(II) complexes (Pt–Ar) are essentially associated with the platinum-cyclometalated unit. Room-temperature emission of the Pt–Ar complexes was attributed to phosphorescence in agreement with DFT calculations. Broad nanosecond (ns)-transient absorption spectra were observed with decays approximately identical to those obtained from the emi…
Fluorescent Type II Materials from Naphthylmethyl Polyamine Precursors
2004
Speciation studies in aqueous solution on the interaction of Cu2+ and Zn2+ with a series of polyaminic ligands N-naphthalen-1-ylmethyl-N′-{2-[(naphthalen-1-ylmethyl)-amino]-ethyl}-ethane-1,2-diamine (Ll), N-naphthalen-1-ylmethyl-N′-(2-{2-[(naphthalen-1-ylmethyl)-amino]-ethylamino}-ethyl)-ethane-1,2-diamine (L2) and N-naphthalen-1-ylmethyl-N′-[2-(2-{2-[(naphthalen-1-ylmethyl)-amino]-ethylamino}-ethylamino)-ethyl]-ethane-1,2-diamine (L3) containing two naphthylmethyl groups at their termini and N 1-(2-{2-[(naphthalen-1-ylmethyl)-amino]-ethylamino}-ethyl)-ethane-1,2-diamine (L4) containing just one naphthylmethyl group have been carried out at 298.1 K in 0.15 mol dm−3 NaCl. In the case of the …
Spectroscopy and Coordination Chemistry of a New Bisnaphthalene−Bisphenanthroline Ligand Displaying a Sensing Ability for Metal Cations
2005
A new fluorescent macrocyclic structure (L1) bearing two naphthalene units at both ends of a cyclic polyaminic chain containing two phenanthroline units was investigated with potentiometric and fluorescence (steady-state and time-resolved) techniques. The fluorescence emission spectra show the simultaneous presence of three bands: a short wavelength emission band (naphthalene monomer), a middle emission band (phenanthroline emission), and a long-wavelength band. All three bands were found to be dependent on the protonation state of the macrocyclic unit (including the polyaminic and phenanthroline structures). The existence of the long-wavelength emission band is discussed and is shown to im…
Ground and excited state properties of polyamine chains bearing two terminal naphthalene units
2002
A series of compounds bearing two naphthalene units linked through methylene groups to both ends of different open-chain polyamines has been investigated. The fluorescence emission studies show the presence of an excimer species whose formation depends on the protonation state and length of the polyamine chains and implies the existence of a bending movement in the excited state allowing the two naphthalene units to approach and interact. This interpretation was clearly proven by time-resolved fluorescence with the appearance of double exponential decays with a rise time observed at the excimer emission wavelength. For comparison purposes one bis-chromophoric compound containing a rigid cha…
Energy transfer between polyamine chains bearing naphthalene terminal units and k3[Co(CN)6]: An example of a molecular photoreactor
2002
Molecular photoreactors consisting of polyamine chains (receptors) bearing terminal naphthalene units (antennae) are described. The receptors are used to bind the substrate hexacyanocobaltate(III) and the antennae to transfer energy to the complex and thus promote a photoaquation reaction.
A New ZnIITweezer Pyridine-Naphthalene System - An Off-On-Off System Working in a Biological pH Window
2005
Their basic idea consisted of the connec-tion of an amine to a fluorophoric anthracene unit on oneside and to a pyridine moiety on the other. At acidic pHvalues the amino and the pyridine groups are protonatedand a photoinduced electron transfer (PET) occurs fromthe π-π* excited state of the anthracene to the protonatedpyridinium unit, leading to quenching of the fluorescence.However, at high pH values, where the amino group is notprotonated, PET alternatively takes place from the aminelone pair to the same excited state of the fluorophore, yield-ing the same inhibitory effect on the fluorescence. Betweenthese two pH values, there is a pH window where PET doesnot take place and fluorescence…
Polyamines containing naphthyl groups as pH-regulated molecular machines driven by light
2001
A series of compounds made up by linking methylnaphthalene fragments at both ends of different polyamine chains have shown to behave as pH-regulated molecular machines driven by light and fluorescence emission studies have proved the formation of an excimer between the two naphthalene units whose appearance, fluorescence intensity and decay times depend on the pH value of the media. Albelda Gimeno, Maria Teresa, Teresa.Albelda@uv.es ; Garcia-España Monsonis, Enrique, Enrique.Garcia-Es@uv.es ; Soriano Soto, Concepción, Concepcion.Soriano@uv.es
CCDC 1970146: Experimental Crystal Structure Determination
2020
Related Article: Ariadna Lázaro, Carla Cunha, Ramon Bosque, João Pina, Jas S. Ward, Khai-Nghi Truong, Kari Rissanen, João Carlos Lima, Margarita Crespo, J. Sérgio Seixas de Melo, Laura Rodríguez|2020|Inorg.Chem.|59|8220|doi:10.1021/acs.inorgchem.0c00577
CCDC 1970147: Experimental Crystal Structure Determination
2020
Related Article: Ariadna Lázaro, Carla Cunha, Ramon Bosque, João Pina, Jas S. Ward, Khai-Nghi Truong, Kari Rissanen, João Carlos Lima, Margarita Crespo, J. Sérgio Seixas de Melo, Laura Rodríguez|2020|Inorg.Chem.|59|8220|doi:10.1021/acs.inorgchem.0c00577
CCDC 1970145: Experimental Crystal Structure Determination
2020
Related Article: Ariadna Lázaro, Carla Cunha, Ramon Bosque, João Pina, Jas S. Ward, Khai-Nghi Truong, Kari Rissanen, João Carlos Lima, Margarita Crespo, J. Sérgio Seixas de Melo, Laura Rodríguez|2020|Inorg.Chem.|59|8220|doi:10.1021/acs.inorgchem.0c00577