**4. Characteristic of technetium-99m for labeling**

More than 85% of radiopharmaceuticals which are being used to diagnose the cancer and infection are 99mTc labeled. The reason for using the 99mTc is due to following characteristics:


electrons by 4d orbital. Different types of ligands which are used to label the technetium and chemical conditions under which labeling process is accomplished are responsible for steadiness of such types of oxidation state. It is observed that technetium is found in nature in the form of halides (TcF6, TcCl6 and TcBr4, oxide,

**Properties of technetium Values** Atomic number 43 Atomic mass (amu) 98

*Single-Photon Emission Computed Tomography (SPECT) Radiopharmaceuticals*

Density gm/cm<sup>3</sup> (at 25°C) 11.5

Melting point in Kelvin 2430.15 Boiling point in Kelvin 5150.15 Occurrence Solid state (naturally)

Electronagetivity 1.9

Electron affinity (kJ/mol) 58 Heat of vaporization kJ/mol 660 Group VIIB (7) Metal category Transitions metal Period Fifth Color Silvery gray Numbers of isotopes Twenty-two

Oxidation state �3, �1, 0, +1,+2,+3,+4,+5,+6,+7 (+4 and +7

First, second, and third ionization energy (kJ/mol) 702, 1472, and 2850, respectively

,2s<sup>2</sup> ,2p<sup>6</sup> ,3s<sup>2</sup> ,3p<sup>6</sup>

,3d10,4s2

are more stable)

,4p6 ,4d6 ,5s<sup>1</sup>

Electronic configuration 1s2

*DOI: http://dx.doi.org/10.5772/intechopen.93449*

states). Oxidation states of smaller values such as �1, +2, +3 are naturally stabilized during complex formation with varieties of ligands; for example, +3 oxidation state is stabilized by the chelating agent, methylene diphosphate [9]. Without the use of these chelating agents in complex formation, the oxidation state will not remain constant and technetium would oxidize to +4 oxidation state and eventually change to +7 oxidation state which is most stable state in complex. The +5 and +6 oxidation of technetium is habitually charged to +4 and +7 oxidation states as shown in the following Eqs. 1 and 2 which is most stable regardless of their proportion.

The coordination number of the technetium during complex formation can be

Technetium generated by Moly generator presents in the form of sodiumpertechnetate (99mTc-NaTcO4). In this pertechnetate ion, the oxidation state of

� in +4 to +7 oxidation

3Tcþ<sup>5</sup> 2Tcþ4<sup>þ</sup> Tcþ<sup>7</sup> (1)

3Tcþ<sup>6</sup> Tcþ<sup>4</sup> <sup>þ</sup> 2Tcþ<sup>7</sup> (2)

�

[TcO2, Tc2O7], sulfides [Tc2S7], and pertechnetate 99mTcO4

*Physical and chemical properties of technetium.*

**6. Reducing agents and reduction of 99mTcO4**

changed between 4 and 9.

**7**

**Table 4.**

