Targeted protein degradation is an innovative strategy in chemical biology and drug discovery that leverages the induced proximity of a ubiquitin E3 ligase to a target protein, facilitating the polyubiquitination and subsequent degradation of the target. This pharmacological strategy employs bifunctional molecules known as Proteolysis Targeting Chimeras (PROTACs), which work via a catalytic, sub-stoichiometric mechanism to eliminate disease-causing proteins from the cell. This mechanism of action distinguishes PROTACs from traditional inhibitors, which block a protein's activity by binding to its functional site, offering advantages such as reduced dosing requirements and prolonged effects. PROTACs comprise a ligand that binds to a target protein and another that recruits the E3 ubiquitin ligase, connected by a linker (Figure ). The linker plays a critical role in bringing the target protein and the ligase into the suitable proximity to form a stable and favourable ternary complex. This enables high potency and selectivity of ligase-directed target ubiquitination and subsequent degradation. The design and length of the linker are crucial, as these parameters not only impact ternary complex formation but ultimately influence the PROTAC's physicochemical properties. Recent efforts have increasingly focused on understanding and optimising PROTAC linkers to unlock their full therapeutic potential. The growing body of research and publications from both drug discovery and academic settings highlights the central role of the linker in PROTAC design and refinement, a field of study often referred to as "linkerology". This discipline involves careful consideration of factors such as linker chemical composition, length, and flexibility. Historically, PROTAC linkers have been composed of linear PEG (i.e., MZ1, Figure ) or alkyl chains (i.e., dBET6, Figure ) of varying lengths. However, recent advances have introduced more complex linker designs, including rigid cyclic structures, heterocyclic scaffolds, spiro and bridged rings, alkynes, ionizable tertiary amines, fluorine atoms, and chiral centres. These unconventional motifs are being investigated not only to enhance PROTAC activity but also to fine-tune their pharmacokinetic properties, including solubility, lipophilicity, intracellular and metabolic stability, and oral bioavailability. Similarly, the development of creative and diversified linkers, including the integration of other chemical modalities like macrocycles (i.e., MacroPROTAC-1, Figure ), or multivalent chemical architectures (i.e., SIM1 and AB3067, Figure ) is also gaining attention. Linkerology allows the optimisation of the properties and activity of degraders, while also offering a fertile ground for medicinal chemistry experimentation to address current PROTACs limitations. A significant challenge for PROTACs development remains their poor cellular permeability/uptake and proneness to transporter-mediated efflux, usually stemming from their high molecular weight and large exposed polar surface area due to linear structures. To tackle this issue, we and others have explored strategies including enhancing linker lipophilicity, replacing amides with esters (i.e., OMZ1 , Figure ) and altering linker composition to influence the conformational dynamics of PROTACs. Indeed, specific linker designs can enable PROTACs to act as molecular chameleons, adopting more compact conformations in response to environmental conditions. This molecular feature has the potential to enhance compounds' drug-like properties, thereby improving their cellular permeability and reducing the efflux ratio. While the concept of molecular chameleons was introduced in the 1970s, interest in this concept has grown significantly as drug discovery shifts toward novel chemical modalities. These modalities, such as PROTACs, exist in a chemical space beyond traditional small-molecule drugs and the rule of five, and their druglike properties are partially attributed to their "molecular chameleon" properties, enabling them to adapt different conformations in diverse environments. In this work, we present the development of ferrocene-PROTACs (FerroTACs), a novel strategy to bias PROTACs` chameleonicity through the rational incorporation of an unconventional linker motif. Central to this design is the use of ferrocene, an organometallic moiety with distinctive structural and functional properties.