A methodological study is presented dealing with carbopalladation reactions on BODIPY dyes bearing aryl-halogen functions. Using this technique, several ester and amide groups were efficiently introduced on the dyes. These changes do not affect the optical properties of the dyes, and thus allow the construction of new BODIPY-based functional dyes with carboxylic anchoring groups or peptide links.

New synthetic methodologies for the efficient chemical conversion of hydrophobic fluorescent dyes into bioconjugable and water-soluble derivatives are described. The combined use of an original sulfonated terminal alkyne and a metal-mediated reaction, namely the copper-catalysed Huisgen 1,3-dipolar cycloaddition ("click" reaction) or the Sonogashira cross-coupling, is the cornerstone of these novel post-synthetic sulfonation approaches.

A series of water-soluble red-emitting distyryl-borondipyrromethene (BODIPY) dyes were designed and synthesized by using three complementary approaches aimed at introducing water-solubilizing groups on opposite faces of the fluorescent core to reduce or completely suppress self-aggregation. An additional carboxylic acid functional group was introduced at the pseudo-meso position of the BODIPY scaffold for conjugation to amine-containing biomolecules/biopolymers. The optical properties of these dyes were evaluated under simulated physiological conditions (i.e., phosphate-buffered saline (PBS), pH 7.5) or in pure water. The emission wavelength (λ(max)) of these labels was found in the 640-660 nm range with quantum yields from modest to unprecedentedly high values (4 to 38 %). The bioconjugation of these distyryl-BODIPY dyes with bovine serum albumin (BSA) and the monoclonal antibody (mAb) 12A5 was successfully performed under mild aqueous conditions.

The synthesis, photophysical characterization and energy-transfer features of a series of hybrid truxene derivatives peripherally decorated with inorganic Os-containing polypyridine units and organic Bodipy dyes are reported. The photoactive terminal units are coupled to the central truxene scaffold by rigid ethynyl linkers in a star-shaped arrangement. The absorption range widely covers the UV-Vis spectrum and the Os (3)MLCT or the Bodipy triplet act as final collectors of the absorbed energy.

An efficient protocol for the direct synthesis of 3 and 3,5-substituted Bodipy derivatives via electrophilic attack with NBS was developed. Various subsistent like ethers, sugar, hydroxyl, thiophen, sulfur, azide, tertiary amines, alkyne, vinyl or phosphonate groups were obtained in moderate to excellent yields. The amine substituted derivatives display unusual spectroscopic and electrochemical properties which were analyzed in solution in the presence of HClg. The diethylamino substituted derivative has a proton association constant of Log beta = 4.7 and the disubstituted derivative two association constants of Log beta = 6.2 and 12.1 in ethanol. In both cases the quenching of the fluorescence is explain by photo-induced electron transfer from the tertiary amine to the Bodipy excited state.

Red- and blue-absorbing boron dipyrromethene dyes, bearing opposite electronic charges, associate in solution to form a 1:2 complex having a stability constant of ca. 1017 M-2. The complex can be dismantled by addition of a large excess of tetra-N-butylammonium cations. The same complex displays liquid crystalline properties on heating from rt to above 150°C, as characterized by various experimental techniques. Highly efficient electronic energy transfer from the red to the blue dye occurs in both the initial complex and in the subsequent mesomorphic state.

The synthesis, characterization, photophysics, and time-dependent density functional theory (TD-DFT) calculations of spirobifluorene-bipyridine based iridium(III), osmium(II), and mixed Ir/Os complexes are presented. The preparation of the reference and mixed complexes proceeded step-by-step and microwave irradiation facilitated the complexation of osmium. The absorption of the target heterobimetallic derivative, Ir-L-Os, is described by linear combination of half of the absorption spectra of the homobimetallic analogues, Ir-L-Ir and Os-L-Os, due to the occurrence of mixed ligand and metal based transitions when the spirobifluorene-(bpy)(2) bridging ligand L is linked to the metal, confirming a negligible interaction between the substituted metallic chromophores. TD-DFT calculations on monometallic, homo- and hetero-bimetallic complexes fully disentangled the origin of the absorption features. Noticeably, in the mixed Ir-L-Os complex an almost quantitative energy transfer from the (3)Ir to the (3)Os MLCT state is occurring, with a rate constant of 4.1 × 10(8) s(-1) and nearly exclusively via a Dexter-type mechanism mediated by the orbitals of the spiroconjugated ligand. This result, together with the outcomes of the TD-DFT calculations, supports the existence of spiroconjugation and evidences the interesting role of this kind of bridge in the energy transfer dynamics of the arrays. In all the complexes, moreover, the ligand fluorescence is heavily quenched by energy transfer processes toward the metallic appended units; the rate constant is estimated in the order of 10(10) s(-1) for Ir-L-Os and higher than 10(12) s(-1) for the other complexes. In the heterometallic array, both at room temperature and at 77 K, all photons are thus funneled to the emissive Os (3)MLCT state, which acts as energy trap for the antenna cascade.

Fluorescent nanorods: Donor-acceptor dyads based on novel unsymmetrically disubstituted closo-1,12-dicarbadecaboranes have been prepared in a completely controlled manner by using a three-step procedure. Dyads with different donor-acceptor spacing were thereby obtained. Efficient energy transfer from the donor to the acceptor was determined in fluid solution at room temperature.

Complexation of boron trifluoride by a series of electron donor/acceptor substituted 2-(2'-hydroxy phenyl)benzoxazole (HBO) derivatives yields luminescent B(III) complexes with an emission wavelength ranging from 385 to 425 nm in dichloromethane or toluene. Appropriate chemical functionalization of these new dyes allows connection to different photoactive subunits (Boranil, BODIPY), endowing an efficient cascade energy transfer.

A sophisticated model of the natural light-harvesting antenna has been devised by decorating a C60 hexa-adduct with ten yellow and two blue boron dipyrromethene (Bodipy) dyes in such a way that the dyes retain their individuality and assist solubility of the fullerene. Unusually, the fullerene core is a poor electron acceptor and does not enter into light-induced electron-transfer reactions with the appended dyes but ineffective electronic energy transfer competes with fluorescence from the yellow dye. Intra-particle electronic energy transfer from yellow to blue dyes can be followed by steady-state and time-resolved fluorescence spectroscopy and by excitation spectra for isolated C60 nano-particles dissolved in dioxane at 20 0C and at 77K. The decorated particles can be loaded into polymer films by spin coating from solution. In the dried film, efficient energy transfer occurs such that photons absorbed by the yellow dye are emitted by the blue dye. Films can also be prepared to contain C60 nano-particles loaded with the yellow Bodipy dye but lacking the blue dye and, under these circumstances, electronic energy migration occurs between yellow dyes appended to the same nano-particle and, at higher loading, to dye molecules on nearby particles. Doping these latter polymer films with the mixed-dye nano-particle coalesces these multifarious processes in a single system. Thus, long-range energy migration occurs among yellow dyes attached to different particles before trapping at a blue dye. In this respect, the film resembles the natural photosynthetic light-harvesting complexes, albeit at much reduced efficacy. The decorated nano-particles sensitize amorphous silicon photocells.