The crucial role of solubilization and crystallization steps in the vibrational and optical properties of {Ta6Bri12} cluster core containing systems.

The high potential of [{Nb 6 Cl i 12 }L a 6 ] cluster-based building blocks as near-infrared radiation blockers for energy saving applications is exposed in the present paper (i = inner edge-bridging ligand, a = apical ligand of the Nb 6 ; L = H 2 O and/or Cl). To do so, a combined experimental and theoretical investigation of edge-bridged [{Nb 6 Cl i 12 }Cl a 6−x (H 2 O) x ] m+/0/n− cluster unit series (x = 0, 4, 6; m = 2, 3, 4; n = 2, 3, 4) has been carried out. By using the K 4 [{Nb 6 Cl i 12 }Cl a 6 ] starting solid-state precursor, we explored the behavior of the [{Nb 6 Cl i 12 }Cl a 6 ] 4− cluster unit during the different steps of its integration as a building block into a polyvinylpyrrolidone (PVP) matrix to form a glass coating composite denoted {Nb 6 Cl i 12 } m+ @PVP (m = 2 or 3). The optical, vibrational and redox properties [{Nb 6 Cl i 12 }Cl a 6−x (H 2 O) x ] m+/0/n− building blocks have been interpreted with the support of electronic structure calculations and simulation of properties. The chemical modifications and oxidation properties have been identified and studied thanks to various techniques in solution. Combining Raman and ultraviolet−visible spectroscopies, electrochemistry, and quantum chemical simulations, we bring new knowledge to the understanding of the evolution of the properties of the [{Nb 6 Cl i 12 }Cl a 6−x (H 2 O) x ] m+/0/n− cluster units as a function of the number of valence electron per cluster (VEC) and the nature of terminal ligands (x = 0, n = 4; x = 4, charge = 0; x = 6, m = 4). The fine understanding of the physical properties and vibrational fingerprints depending on the VEC and chemical modifications in solution are mandatory to master the processing of cluster-based building blocks for the controlled design and shaping of glass coating nanocomposites. On the basis of this acquired knowledge, [{Nb 6 Cl i 12 }Cl a 6−x (H 2 O) x ] m+/0/n− building blocks were embedded in a PVP matrix. The resulting {Nb 6 Cl i 12 } 2+ @PVP nanocomposite film shows excellent ultraviolet (UV, 280−380 nm) and near-infrared (NIR, 780−1080 nm) blocking ability (>90%) and a highly visible light transmittance thanks to the controlled integration of the {Nb 6 Cl i 12 } 2+ cluster core. The figures of merit (FOM) value of T vis /T sol (T vis = visible transmittance and T sol = solar transmittance) as well as the haze, clarity, and the NIR shielding values (S NIR ) were measured. After optimization of the integration process, a {Nb 6 Cl i 12 } 2+ @PVP nanocomposite on glass substrate has been obtained with a high FOM equal to 1.29. This high value places the transparent green olive {Nb 6 Cl i 12 } 2+ @PVP nanocomposites at the top system in the benchmark in the field of glass coating composites for energy-saving applications.

This review is dedicated to various functional nanoarchitectonic nanocomposites based on molecular octahedral metal atom clusters (Nb 6 , Mo 6 , Ta 6 , W 6 , Re 6 ). Powder and film nanocomposites with two-dimensional, one-dimensional and zero dimensional morphologies are presented, as well as film matrixes from organic polymers to inorganic layered oxides. The high potential and synergetic effects of these nanocomposites for biotechnology applications, photovoltaic, solar control, catalytic, photonic and sensor applications is demonstrated. This review also provides a basic level of understanding how nanocomposites are characterized and processed using different technics and methods. The main objective of this review would be to provide guiding significance for the design of new high-performance nanocomposites based on transition metal atom clusters.

The antagonism between global energy needs and the obligation to slow global warming is a current challenge. In order to ensure sufficient thermal comfort, the automotive, housing and agricultural building sectors are major energy consumers. Solar control materials and more particularly, selective glazing are part of the solutions proposed to reduce global energy consumption and tackle global warming. In this context, these works are focused on developing new highly ultraviolet (UV) and near-infrared (NIR) absorbent nanocomposite coatings based on K4[{Nb6-xTaxXi12}Xa6]. (X = Cl, Br, 0 ≤ x ≤ 6) transition metal cluster compounds. These compounds contain cluster-based active species that are characterized by their strong absorption of UV and NIR radiations as well as their good transparency in the visible range, which makes them particularly attractive for window applications. Their integration, by solution processes, into a silica-polyethylene glycol or polyvinylpyrrolidone matrices is discussed. Of particular interest is the control and the tuning of their optical properties during the integration and shaping processes. The properties of the solutions and films were investigated by complementary techniques (UV-Vis-NIR spectrometry, ESI-MS, SEM, HRTEM, etc.). Results of these works have led to the development of versatile solar control coatings whose optical properties are competitive with commercialized material.

The development of highly ultraviolet (UV) and near-infrared (NIR) absorbent transparent coatings is an important enabling technology and area of research for environmental sustainability and energy conservation. Different amounts of K 4 [{Nb 5 TaX i 12 }X a 6 ] cluster compounds (X = Cl, Br) dispersed into polyvinylpyrrolidone matrices were prepared by a simple, nontoxic and low-cost wet chemical method. The resulting solutions were used to fabricate visibly transparent, highly UV and NIR absorbent coatings by drop casting. The properties of the solution and films were investigated by complementary techniques (optical absorption, electrospray ionization mass spectrometry and Raman spectroscopy). The UV and NIR absorption of such samples strongly depended on the concentration, dispersion and oxidation state of the [{Nb 5 TaX i 12 }X a 6 ] nanocluster-based units. By varying and controlling these parameters, a remarkable improvement of the figures of merit T L /T E and S NIR for solar-glazing applications was achieved compared to the previous results on nanocomposite coatings based on metal atom clusters.

New nanocomposite materials with UV-NIR blocking properties and hues ranging from green to brown were prepared by integrating inorganic tantalum octahedral cluster building blocks prepared via solid-state chemistry in a PMMA matrix. After the synthesis by the solid-state chemical reaction of the K4[{Ta6Bri12}Bra6] ternary halide, built-up from [{Ta6Bri12}Bra6]4− anionic building blocks, and potassium cations, the potassium cations were replaced by functional organic cations (Kat+) bearing a methacrylate function. The resulting intermediate, (Kat)2[{Ta6Bri12}Bra6], was then incorporated homogeneously by copolymerization with MMA into transparent PMMA matrices to form a brown transparent hybrid composite Ta@PMMAbrown. The color of the composites was tuned by controlling the charge and consequently the oxidation state of the cluster building block. Ta@PMMAgreen was obtained through the two-electron reduction of the [{Ta6Bri12}Bra6]2− building blocks from Ta@PMMAbrown in solution. Indeed, the control of the oxidation state of the Ta6 cluster inorganic building blocks occurred inside the copolymer, which not only allowed the tuning of the optical properties of the composite in the visible region but also allowed the tuning of its UV and NIR blocking properties.