Metallodendrimer
Image:54-ferrocene dendrimer.png
A metallodendrimer is a type of dendrimer with incorporated metal atoms. The development of this type of material is actively pursued in academia.{{Cite journal| last1 = Gorman | first1 = C.| year = 1998| title = Metallodendrimers: Structural Diversity and Functional Behavior| journal = Advanced Materials| volume = 10| issue = 4| pages = 295–309 | doi = 10.1002/(SICI)1521-4095(199803)10:4<295::AID-ADMA295>3.0.CO;2-N}}{{Cite journal| doi = 10.1016/S0010-8545(99)00036-3| title = Organometallic dendrimers with transition metals | first5 = J. | last5 = Losada | first4 = B.| last4 = Alonso | first3 = C. M.| last3 = Casado | first2 = M. S.| year = 1999| last2 = Morán| last1 = Cuadrado | first1 = I.| journal = Coordination Chemistry Reviews| volume = 193-195| pages = 395–445 }}{{Cite journal| doi = 10.1016/S0277-5387(99)00301-0| title = Metal-containing dendritic polymers | first2 = T.| year = 1999| last2 = Welton| last1 = Stoddart | first1 = F.| journal = Polyhedron| volume = 18| issue = 27| pages = 3575 | hdl = 10044/1/9945 | hdl-access = free}}
Structure
The metal can be situated in the repeat unit, the core or at the extremities as end-group. Elements often encountered are palladium and platinum. These metals can form octahedral six-coordinate M(IV) linking units from organic dihalides and the corresponding 4-coordinate M(II) monomers. Ferrocene-containing dendrimers and dendrimers with cobaltocene and arylchromiumtricarbonyl units have been reported in end-functional dendrimers.
Metallodendrimers can form as metal complexes with dendritic counter ions for example by hydrolysis of ester terminated PAMAM dendrimers with sodium hydroxide.
Applications
Metallodendrimers are investigated as equivalents to nanoparticles. Applications can be expected in the fields of catalysis, as chemical sensors in molecular recognition - for example of bromine and chloride anions {{Cite journal| doi = 10.1002/(SICI)1521-3773(19990614)38:12<1747::AID-ANIE1747>3.0.CO;2-G| title = A Polycationic Metallodendrimer with 24 [Fe(η5-C5Me5)(η6-N-Alkylaniline)]+ Termini That Recognizes Chloride and Bromide Anions| year = 1999| last1 = Valério | first1 = C.| last2 = Alonso | first2 = E.| last3 = Ruiz | first3 = J.| last4 = Blais | first4 = J. C.| last5 = Astruc | first5 = D.| journal = Angewandte Chemie International Edition| volume = 38| issue = 12| pages = 1747 }} - or as materials capable of binding metals. Metallodendrimers can also mimic certain biomolecules for example haemoprotein in dendrimer with a porphyrin core. Further uses are reported as electrocatalyst.{{Cite journal| doi = 10.1021/cm010854y| title = Nanocomposite Multilayer Film of a Ruthenium Metallodendrimer and a Dawson-Type Polyoxometalate as a Bifunctional Electrocatalyst| year = 2002| last1 = Cheng | first1 = L.| last2 = Cox | first2 = J. A.| journal = Chemistry of Materials| volume = 14| pages = 6–8 }}{{Cite journal| doi = 10.1021/ac0105585| title = Carbon Electrodes Modified with Ruthenium Metallodendrimer Multilayers for the Mediated Oxidation of Methionine and Insulin at Physiological pH| year = 2001| last1 = Cheng | first1 = L.| last2 = Pacey | first2 = G. E.| last3 = Cox | first3 = J. A.| journal = Analytical Chemistry| volume = 73| pages = 5607–5610| pmid = 11816594| issue = 22 }}
Examples of metallodendrimer heterogeneous catalysis are a nickel-containing dendrimer active in the Kharasch addition,{{Cite journal| doi = 10.1038/372659a0| title = Homogeneous catalysts based on silane dendrimers functionalized with arylnickel(II) complexes| year = 1994| last1 = Knapen | first1 = J. W. J.| last2 = Van Der Made | first2 = A. W.| last3 = De Wilde | first3 = J. C.| last4 = Van Leeuwen | first4 = P. W. N. M.| last5 = Wijkens | first5 = P.| last6 = Grove | first6 = D. M.| last7 = Van Koten | first7 = G.| journal = Nature| volume = 372| pages = 659 |bibcode = 1994Natur.372..659K | issue=6507| hdl = 1874/6274| hdl-access = free}} palladium-containing dendrimers active in ethylene polymerization{{Cite journal| doi = 10.1016/S0022-328X(03)00173-6| title = The synthesis and catalytic activity of a first-generation poly(propylene imine) pyridylimine palladium metallodendrimer | first3 = S.| last3 = Mapolie | first2 = R.| year = 2003| last2 = Chen| last1 = Smith | first1 = G.| journal = Journal of Organometallic Chemistry| volume = 673| issue = 1–2 | pages = 111–035 }} and in the Heck reaction.{{Cite journal| doi = 10.1016/j.molcata.2003.12.010| title = Iminopyridyl-palladium dendritic catalyst precursors: evaluation in Heck reactions | first2 = S. F.| year = 2004| last2 = Mapolie| last1 = Smith | first1 = G.| journal = Journal of Molecular Catalysis A: Chemical| volume = 213| issue = 2| pages = 187–192 }}