Conclusion

Scheme 1 L1 is used as ligand in this Chapter

2.11. Conclusion

In conclusion, it is evident that the probe L1 is unique in its kind and highly selective in its recognising properties towards Pd²⁺ ions have established itself as a potentially applicable sensor that not only detects Pd²⁺ ion in solution but also in living cells with high accuracy.

The limit of detection (0.210 M) of L1 is found to be far less than the international standard prescribed by the WHO (47–94 M). The probe remains intact after several cycles of using as a sensor, which is proved by the reversibility studies performed with Na2EDTA. The stability of L1–Pd(II) complex is very high and it is not affected by the presence any counter anions as examined. The probe was able to perform in water samples taken from various natural sources within the pH range of 2–8. The paper strip test and TLC plate test prove the practical applicability of L1 for spot tests which makes it easy to use for all practical purposes. The lifetime decay profile of the probe and the complex shows the static nature of quenching which further confirms the complex formation in solution. Theoretical calculations show a decrease in energies of HOMO, LUMO as well as the energy gap between them, consistent with experimentally observed red shift in the complex. A 5 M solution of L1 showed low cytotoxicity towards L929 cells and hence it can be used for detection of Pd²⁺

ion in living cells by fluorescence quenching phenomenon. In essence, the probe L1 can be used as an excellent sensor for Pd²⁺ ion in every practical aspect.

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Appendix:

Table A1 Comparison of recent fluorescent probes for Pd²⁺ ion.

Probe λem(nm) LOD Application Solvent Ref.

580

“Turn-on”

0.200μ M

In PC12 cells.

Tris–HCl aqueous

buffer solutions with 1% ethanol as co-solvent.

9

480

Ratiometric 0.07μM

In live RAW 264.7 macrophage

cells.

20 mM phosphate buffer saline

(PBS), pH 7.4).

11

567

“Turn - on”

0.1 ppm

In Hct 116 cells.

aq. HEPES buffer–

acetonitrile (1 : 1, v/v; pH

7.2)

14

Chapter 2

53 530

“Turn - off”

0.34 ppm

In living HeLa cells.

aqueous acetonitrile

solution (CH3CN : H2O = 4 : 1,

v/v).

30

406

“Turn - off”

0.93 μM

In HEK-293 and L929

cell.

HEPES buffer containing 1% DMF (10

mM, pH = 7.2)

38

370

“Turn - off” 13.3μM

In Artemiasali

na.

CH3CN/

H2O (1/1 (v/v) HEPES=50 mM, pH=7.4

40

454

“Turn - off”

0.210

μM In Hela and L929 cells.

MeOH / HEPES buffered aqueous solution (5 mM, pH = 7.4, 6:4, v/v)

This work

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Fig. A1 Experimental mass spectrum of [Pd(L1)Cl(CH3CN)]⁺ complex ion.

Fig. A2 Theoretical mass spectrum of [Pd(L1)Cl(CH3CN)]⁺ complex ion using mMass software.

Chapter 2

55

Fig. A3 Experimental and simulated UV-Vis absorption spectra of L1 and its complex with Pd²⁺ ion.

L1 L1 + PdCl2

Fig. A4 Images TLC plate test under longer UV light.

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Chapter 3

Chapter 3

56

3-(2-Hydroxyphenyl)imidazo[5, 1-a]isoquinoline as Cu(II)