General

All the reactions were carried out under an inert atmosphere using dry argon. Fluorescein (free acid) 1 a, iron (II, III) oxide nanopowder, 50–100 nm particle size, 97 % trace metals basis 4 a, aluminum oxide nanopowder, <50 nm particle size 4 b, copper (II) oxide nanopowder,<50 nm particle size 4 c, titanium (IV) oxide nanopowder, 21 nm particle size, >99.5 % trace metal basis 4 d, silicon dioxide nanopowder, 5–20 nm particle size, 99.5 % trace metal basis 4 e and titanium silicon oxide nanopowder, <50 nm particle size, 99.8 % trace metal basis 4 f, were purchased from Sigma Aldrich. All other chemical reagents were used without further purification as purchased from Aldrich, Merck, and HiMedia unless otherwise specified. The solvents, namely, DMF, ethyl acetate, hexane, DCM, DMSO, ethanol, THF, toluene, and diethyl ether, were dried and deoxygenated by bubbling with argon gas for 30 minutes. Thin-layer chromatography (TLC) was performed on aluminum sheets coated with silica gel 60 F254 and revealed using a UV lamp. NMR (1H: 600 MHz, 13C: 150 MHz) spectra were recorded on Bruker BioSpin GmbH 600 MHz spectrometer using DMSO as a solvent with the chemical shifts (δ) given in ppm and referred to tetramethylsilane (TMS). UV-Vis spectra were recorded on Shimadzu UV1800 spectrophotometer. Photoluminescence (PL) spectra were recorded on an Agilent G9800 Cary Eclipse Fluorescence spectrophotometer. X-ray Photoelectron Spectroscopy (XPS) data were recorded on a Thermo ESCALAB 250 Xi using a monochromatic Al Kα-radiation source (1486.6 eV) with a spot size of 850 μm. Spectra acquisition and processing were carried out using the software Thermo Advantage Version 4.87. The base pressure in the XPS analysis chamber was in the range 10−10 to 10−9 Torr. The analyzer was operated with pass energy of 20 eV, dwell time of 50 min, and with a step size of 0.1 eV. Thermogravimetric Analysis (TGA) was recorded on Shimadzu TGA-60H (Kyoto, Japan) analyzer and was used to measure the thermal stability of composites from room temperature to 800 °C with a heating rate of 10 °C min−1 under an inert atmosphere using pure nitrogen. FTIR spectra were recorded on Agilent Cary 630 FTIR instrument. Electron impact high-resolution mass spectra (EI-HRMS) were recorded on a Thermo (DFS) with a standard PFK (perfluorokerosene) as lock mass. The analyzed data is converted to accurate mass with the help of X–Calibur accurate mass calculation software.

Synthesis Synthesis of 2 a

2 a was synthesized following the reported procedure21 with: fluorescein 1 a (1 g, 3.0 mmol, 1 equiv.), 1-bromo-2,4-dinitrobenzene (0.7 g, 3.0 mmol, 1 equiv.), K2CO3 (0.46 g, 3.3 mmol, 1.1 eq.), and 30 mL anhydrous DMF mixed in a Schlenk tube under a positive stream of argon and the mixture was stirred at room temperature for 24 h. The reaction mixture was extracted with ethyl acetate from a 0.1 m lithium chloride solution (2×100 mL) and the organic phase was washed with water (3×100 mL). The organic layer was then concentrated and the pure compound was isolated by silica gel column chromatography using ethyl acetate/hexane (30 : 70 by volume) as eluent yielding a yellow solid (80 %); 1H NMR (DMSO-d6, 600 MHz, ppm): δ 10.22 (s, 1H, OH), 8.91 (s, 1H, ArH), 8.49–8.47 (m, 1H, ArH), 8.04–8.03 (d, J=7.2 Hz, 1H, ArH) 7.84–7.73 (m, 2H, ArH), 7.43 (d, J=9 Hz, 2H, ArH), 7.31 (d, J=2.4 Hz, 1H, ArH), 7.01–6.99 (m, 1H, ArH), 6.92 (d, J=9 Hz,1H, ArH), 6.71 (d, J=2.4 Hz, 1H, ArH), 6.61 (d, J=2.4 Hz, 1H, ArH) 6.54 (s, 1H, ArH); 13C NMR (DMSO-d6, 150 MHz, ppm): δ 170.33, 168.52, 159.73, 159.45, 155.80, 155.61, 153.71, 152.25, 151.90, 142.25, 139.97, 130.37, 129.73, 125.79, 124.84, 121.93, 120.96 116.50, 115.68, 113.20, 109.10, 107.98, 102.23, 81.87; EI-HRMS: m/z calculated for (M•+) C26H14N2O9 498.0694 , found 498.0695; UV-Vis: (DMF, 10−6 m), λmax [nm]=457.

Synthesis of 3 a

2 a (0.8 g, 1.6 mmol, 1 equiv.), (chloromethyl)triethoxysilane (0.34 g, 1.6 mmol, 1 equiv.), K2CO3 (0.24 g, 1.8 mmol, 1.1 eq.), and 30 mL anhydrous DMF were added in a Schlenk tube under a positive stream of argon and the mixture was stirred at room temperature for 24 h. The reaction mixture was then extracted with ethyl acetate from a 0.1 m lithium chloride solution (2×100 mL), and the organic phase was washed with water (3×100 m). The organic layer was concentrated, and the pure compound was isolated by suspending in DCM followed by filtration and washed with diethyl ether. Red solid. Yield: (52 %); 1H NMR (DMSO-d6, 600 MHz, ppm): δ 8.92 (s, 1H, ArH), 8.47 (br, 1H, ArH), 8.06–8.04 (m, 1H, ArH) 7.87–7.76 (m, 4H, ArH), 7.42–7.34 (m, 1H, ArH), 7.01–6.96 (m, 2H, ArH), 6.96–6.75 (m, 3H, ArH), 4.34 (t, J=4.8 Hz, 6H, -CH2), 3.87 (s, 2H, -CH2), 1.05 (t, J=6.6 Hz, 9H, -CH3); FTIR [cm−1]: 1390 (N−O), 1043 (C−O), 801 (Si−CH2), 670 (Si−O).

Synthesis of 5 a (Procedure A)

A Schlenk tube was charged with iron (II, III) oxide nanopowder 4 a (69 mg, 0.3 mmol 1 equiv.) and 3 a (100 mg, 0.15 mmol, 0.5 equiv.) in 20 mL anhydrous toluene, and the reaction mixture was refluxed for 12 h under argon. The product was isolated by filtration and washed several times with anhydrous toluene, DCM, THF, and ethanol. Off-white solid (yield: 89 %). UV-Vis: (Ethanol, 10−6 m), λmax [nm]=271 and 512; FTIR [cm−1]: 2094 (Fe3O4 fingerprint), 1390 (N−O), 1043 (C−O), 801 (Si−CH2), 670 (Si−O).

Synthesis of 5 b

5 b was prepared following the procedure A with aluminum oxide nano powder 4 b (30 mg, 0.3 mmol, 1 equiv.) and 3 a (100 mg, 0.15 mmol, 0.5 equiv.) in 20 mL anhydrous toluene. Yellow solid (yield: 83 %). UV-Vis: (Ethanol, 10−6 m), λmax [nm]=271 and 512, FTIR [cm−1]: 3410 (Al2O3 fingerprint),1394 (N−O), 1051 (C−O), 801 (Si−CH2), 670 (Si−O).

Synthesis of 5 c

5 c was prepared following procedure A with copper (II) oxide nano powder 4 c (24 mg, 0.3 mmol, 1 equiv.) and 3 a (100 mg, 0.15 mmol, 0.5 equiv. ) in 20 mL of anhydrous toluene. Grey solid (yield: 81 %). UV-Vis: (Ethanol, 10−6 M), λmax [nm]=271 and 512, FTIR [cm−1]: 2094  1 (CuO fingerprint), 1390 (N−O), 1043 (C−O), 801 (Si−CH2), 670 (Si−O).

Synthesis of 6 a

6 a was prepared following procedure A with titanium silicon oxide nano powder 4 f (40 mg, 0.3 mmol, 1 equiv.) and 3 a (100 mg, 0.15 mmol, 0.5 equiv.) in 20 mL of anhydrous toluene. Yellow solid (yield: 88 %). UV-Vis: (Ethanol, 10−6 M), λmax [nm]=271 and 512, FTIR [cm−1]: 3496 (TiO2-SiO2 fingerprint), 1394 (N−O), 1051 (C−O), 801 (Si−CH2), 659 ( Si−O).

Synthesis of 3 b

2 a (6 g, 12 mmol, 1 equiv.), (3-chloropropyl)trimethoxysilane (2 g, 12 mmol, 1 equiv.), K2CO3 (1.8 g, 13.2 mmol, 1.1 equiv.), and 180 mL of anhydrous DMF were mixed in a Schlenk tube under a positive stream of argon and the mixture was stirred at room temperature for 24 h. The reaction mixture was extracted with ethyl acetate from a 0.1 m lithium chloride solution (2×100 mL) and the organic phase was washed with water (3×100 mL). The organic layer was completely dried and the residue was suspended in water and sonicated before filtration under reduced pressure. The precipitate was washed exhaustively with petroleum ether yielding a red solid (95 %); 1H NMR (CD2Cl2, 600 MHz, ppm): δ 8.72 (s, 1H, ArH), 8.46 (br, 1H, ArH), 8.28–8.24 (m, 1H, ArH) 7.75–7.68 (m, 4H, ArH), 7.32 (br, 1H, ArH), 7.24 (m, 1H, ArH), 6.96 (br, 1H, ArH), 6.86–6.76 (m, 3H, ArH), 4.08 (s, 2H, -CH2), 3.55 (br, 9H, -CH3), 1.86 (br, 2H, -CH2), 0.78 (br, 2H, -CH2) ; 13C NMR (CD2Cl2,150 MHz, ppm): δ 185.56, 165.95, 163.84, 159.27, 157.80, 156.13, 154.60, 134.97, 133.08, 131.42, 130.98, 130.74, 130.02, 129.88, 129.60, 129.37, 122.15, 117.90, 115.27, 114.30, 105.83, 105.65, 101.11, 70.00, 57.99, 47.72, 14.48, 10.29; FTIR [cm−1]: 1394 (N−O), 1051 (C−O), 801 (Si−CH2), 670 (Si−O).

Synthesis of 7 a (Procedure B)

A Schlenk tube was charged with iron (II, III) oxide nano powder 4 a (700 mg, 3.0 mmol, 1 equiv.) and 3 b (1 g, 1.5 mmol, 0.5 equiv.) in 200 mL of anhydrous toluene. The reaction mixture was refluxed for 12 h under argon. The product was isolated by filtration using Millipore®, and the precipitate was washed several times with anhydrous toluene followed by ethanol. Grey solid (yield: 92 %). UV-Vis: (Ethanol, 10−6 m), λmax [nm]=219, 421 and 448; FTIR [cm−1]: 2105 (Fe3O4 fingerprint), 1587 (C−C), 1375 (N−O), 1248 (C−N), 1099 (C−O), 846 (Si−CH2), 659 (Si−O).

Synthesis of 7 b

7 b was prepared following procedure B with aluminum oxide nano powder 4 b (300 mg, 3.0 mmol, 1 equiv.) and 3 b (1 g, 1.5 mmol, 0.5 equiv.) in 200 mL of anhydrous toluene. Yellow solid (yield: 88 %). UV-Vis: (Ethanol, 10−6 m), λmax [nm]=219, 421 and 448; FTIR [cm−1]: 3373 (Al2O3 fingerprint), 1587 (C−C), 1375 (N−O), 1244 (C−N), 1077 (C−O), 753 (Si−CH2), 663 (Si−O).

Synthesis of 7 c

7 c was prepared following procedure B with copper (II) oxide nano powder 4 c (240 mg, 3.0 mmol, 1 equiv.) and 3 b (1 g, 1.5 mmol, 0.5 equiv.) in 200 mL of anhydrous toluene. Grey solid (yield: 82 %). UV-Vis: (Ethanol, 10−6 m), λmax [nm]=219, 421 and 448; FTIR [cm−1]: 2098 (CuO fingerprint), 1587 (C−C), 1375 (N−O), 1248 (C−N), 1099 (C−O), 846 (Si−CH2), 659 (Si−O).

Synthesis of 7 d

7 d was prepared following procedure B with titanium (IV) oxide nano powder 4 d (240 mg, 3.0 mmol, 1 equiv.) and 3 b (1 g, 1.5 mmol, 0.5 equiv.) in 200 mL of anhydrous toluene. Yellow solid (yield: 87 %). UV-Vis: (Ethanol, 10−6 m), λmax [nm]=219, 421 and 448; FTIR [cm−1]: 3358 (TiO2 fingerprint), 1587 (C−C), 1375 (N−O), 1244 (C−N), 1077 (C−O), 752 (Si−CH2) and 663 (Si−O).

Synthesis of 7 e

7 e was prepared following procedure B with silicon oxide nano powder 4 e (182 mg, 3.0 mmol, 1 equiv.) and 3 b (1 g, 1.5 mmol, 0.5 equiv.) in 200 mL of anhydrous toluene. Yellow solid (yield: 84 %). UV-Vis: (Ethanol, 10−6 m), λmax [nm]=279, 421 and 448; FTIR [cm−1]: 1587 (C−C), 1375 (N−O), 1244 (C−N), 1077 (C−O), 752 (Si−CH2), 663 (Si−O).