**5.1 Activity of ferrocenyl moiety**

*Photophysics, Photochemical and Substitution Reactions - Recent Advances*

*and their molar equivalents of (S)-(blue)(R)-(pink) [66].*

B16 and B3 as shown in **Figures 9** and **10** [60].

**4.3 Chiral recognition of ferrocenyl derivatives**

**5. DNA interaction of ferrocenyl ureas and thioureas**

*Novel redox active ferrocenyl urea receptors for the purpose of binding and sensing the chiral carboxylate anions* 

non-covalent in nature (π⋯H), which intervene supramolecular structures for

Determination of some important biological activities usually depends upon these types of secondary nonbonding interactions between the molecules. Greater ability of compounds to associate with macromolecules such as DNA and proteins is observed due to having an ability to make stronger nonbonding interactions [61]. Among the compounds studied, B16 was reported to be associated with more secondary interactions that were apparent from H-bonding data and formation of a supramolecular structure. Therefore, it can be predictable that B16 can have better strapping interaction with DNA that will transform into more elevated biological

Now a days, main focus in supramolecular chemistry is chiral recognitions [62] hence designing of enantioselective sensors growing quickly. The encouragement directed us to search for appropriate ways of ascertaining one enantiomer of a specific chiral target board regarding its mirror image [63–65] (**Figure 11**).

The productions of chiral urea's series attached to the ferrocene group which is redox active are discovered [62]. These are able to bind through hydrogen bonding interactions with chiral carboxylates in organic solvents confirmed by spectroscopic and cyclic voltammetric measurements. Cyclic voltammetric measurements have shown that these guests can be sensed via electrochemical approaches in solution. For example, enantioselective nature is prominent enough in the association of protected amino acid, i.e., N-benzenesulfonylproline, through a ferrocenyl-benzyl host that permits the contrary enantiomers to be distinguished in an electrochemical way as

DNA is relatively the key target within cells for research work having small molecular entities important biologically, i.e., steroids, cancer-causing agents and other various modules of drugs [67]. The exploration of interactions of drug with DNA is far more imperative for consideration of characteristic molecular drug action mechanisms to its peculiar target and for fabrication of definite DNA-targeted drugs [68]. Usually, three binding approaches, intercalative mode of binding, groove binding, and electrostatic type of interactions, are involved in the noncovalent interactions

**58**

**Figure 11.**

activities [60].

depicted in (**Figure 11**) [66].

The introduction of a ferrocenyl group to molecules like urea and thiourea that bind with DNA is an auspicious strategy to take the ferrocene moiety in close proximity of DNA which most possibly boosts the probability of DNA damage and cell apoptosis. The above-discussed anticancer character of ferrocenyl derivatives is found to be reliant on mainly oxidation state of Fe in ferrocene moiety as approximate results clearly exhibited that the Fe(II) ferrocenyl derivative compound is found to have more activity than Fe(III)-containing compounds [73].

One of the Fe(II) compounds, ferrocifen, performs its action by altering the conformation of protein having receptor site as indicated by the results of the study carried out [74]. Binding of ferrocifen to estrogen receptor (ER) is considered to result in its dimerization, which is followed by attachment of the dimerized species to a particular targeted area of DNA. Reactive oxygen species (ROS), such as hydroxyl radicals (∙OH) produced as a result of electron transfer reactions, result in in-vivo formation of ferrocenium ion or formation of ferrocifen-ER complex. ROS produced can be responsible to damage DNA [75, 76] and may also control the anticancer activity by forming the radical metabolites that carry the biological impairment in cancerous regions [77].
