Metallo-Complexes
Metallo-complexes (MCs) formed by transition metals during interaction with other atoms are of interest for sensor applications because MCs may act as receptors for different types of analytes. It was shown that macrocyclic compounds such as crown ethers,
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Metallo-Complexes
Because transition metals are capable of establishing reversible interactions with other atoms, they can be exploited to form metallo-complexes (MCs), which may act as receptors for different types of analytes. It was shown that macrocyclic compounds such as crown ethers, cyclodextrins, calixarenes, cyclophanes, cavitands, cryptands, spherands, carcerands, cyclopeptides, and other structurally related species can be incorporated in these metallosupramolecules (Atwood et al. 1996). Metal phthalocyanines (MPcs), aromatic macrocyclic compound which have semiconductor properties, can also be referred to as this class of materials (Schollhorn et al. 1998; Fietzek et al. 1999; Ceyhan et al. 2006). Phthalocyanine (Pc) ligands can coordinate with various metal ions, and the central metals can interact with small molecules through a coordination bond (see Fig. 10.1). The phthalocyanines are stable up to 450 °C; at this temperature, the materials decompose but do not melt. Because of their high decomposition temperature, they can be vacuum evaporated to produce thin films. Porphyrin molecules can also be assembled into nanostructures using several methods (Kosal et al. 2002; Medforth et al. 2009). Several reviews are available analyzing the performance of porphyrins and cyanines in gas sensing (Di Natale et al. 1998, 2007; Ozturk et al. 2009; Nardis et al. 2011; Trogler 2012). In metalloporphyrins, metallophthalocyanines, and related macrocycles, gas sensing is accomplished either by p-stacking of the gas into organized layers of the flat macrocycles or by gas coordination to the metal center without the cavity inclusion. In particular, metalloporphyrins provide several mechanisms of gas response including hydrogen bonding, polarization, polarity interactions, metal center coordination interactions, and molecular arrangements (Di Natale et al. 2007; Nardis et al. 2011). Harbeck et al. (2011) and Sen et al. (2011) have shown that metal complexes of vic-dioximes can be characterized as candidate materials for volatile organic compound sensing with sorption-based chemical gas sensors as well. The vic-dioximes are known to form stable complexes with a variety of metals such as Ni2+, Pd2+, Cu2+, Co2+, Zn2+, or Cd2+. Furthermore, they can be modified easily in the substituent structure. Metallodendrimers are representative of metallo-complexes as well (Albrecht and van Koten 1999; Hwang et al. 2007). Metallodendrimers can be categorized (see Fig. 10.2), such as when metal centers are positioned at the infrastructure’s core and connectors positioned between branching centers, or act as terminal groups. Metal centers can also be integrated as structural auxiliary points within the dendritic framework by their incorporation after dendrimer construction. This means that there are numerous combinations in metallo-complexes. It is important that all these supramolecules possess specific host–guest behavior with different luminescent or electronic properties, which can be exploited for sensing purposes. The necessary c
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