In order to explore how specific atom-to-atom replacements change the electrostatic potentials on 1,3,4-chalcogenadiazole derivatives, and to deliberately alter the balance between intermolecular interactions, four target molecules were synthesized and characterized. DFT calculations indicated that the atom-to-atom substitution of Br with I, and S with Se enhanced the σ-hole potentials, thus increasing the structure directing ability of halogen bonds and chalcogen bonds as compared to intermolecular hydrogen bonding. The delicate balance between these intermolecular forces was further underlined by the formation of two polymorphs of 5-(4-iodophenyl)-1,3,4-thiadiazol-2-amine; Form I displayed all three interactions while Form II only showed hydrogen and chalcogen bonding. The results emphasize that the deliberate alterations of the electrostatic potential on polarizable atoms can cause specific and deliberate changes to the main synthons and subsequent assemblies in the structures of this family of compounds.

The amino group of 2-amino-5-(4-halophenyl)-1,3,4-chalcogenadiazole has been replaced with bromo/iodo substituents to obtain a library of four compositionally related compounds. These are 2-iodo-5-(4-iodophenyl)-1,3,4-thiadiazole, C8H4I2N2S, 2-bromo-5-(4-bromophenyl)-1,3,4-selenadiazole, C8H4Br2N2Se, 2-bromo-5-(4-iodophenyl)-1,3,4-selenadiazole, C8H4BrIN2Se, and 2-bromo-5-(4-iodophenyl)-1,3,4-thiadiazole, C8H4BrIN2S. All were isostructural and contained bifurcated Ch...N (Ch is chalcogen) and X...X (X is halogen) interactions forming a zigzag packing motif. The noncovalent Ch...N interaction between the chalcogen-bond donor and the best-acceptor N atom appeared preferentially instead of a possible halogen bond to the same N atom. Hirshfeld surface analysis and energy framework calculations showed that, collectively, a bifurcated chalcogen bond was stronger than halogen bonding and this is more structurally influential in this system.

Introduction The presence of detrusor muscle (DM) is an essential component in "complete" transurethral resection of bladder tumour (TURBT) specimen. This study analyses patients who were subjected to a "complete" first TURBT to determine the presence/absence of DM in the specimen. Methodology Newly diagnosed non-muscle invasive bladder cancer (NMIBC) from 1-April-2007 to 31-March-2017(10-years) were retrospectively analysed at National Hospital of Sri Lanka. All TURBTs performed at initial diagnosis were analysed to determine the presence of DM in the specimen, the recurrence rate at first check cystoscopy (FCC) at 3 months and the association with surgeon's experience. Results Of 181 TURBT, 99(54.7%) were done by Consultant Urological Surgeon (CUS) and 82(45.3%) by senior registrars (SR). The overall DM positivity rate was 59.7% (n= 108/181), for CUS: 63.6% (n=63/99) and SRs 54.9% (n = 4 5 / 8 2) (p = 0. 2 3 2) ; f o r p Ta t u m o u r s :-C U S : 46.5%vs.SRs:50 %(p=0.751) and for pT1 tumours:-CUS: 76.8%vs.SRs:59.5 %(p=0.067). Analysis of those who were followed up (145/181, 80.1%) showed a positive recurrence at FCC in 27.1 %(23/85) and 30.0 %(18/60) when DM was present and absent in the first TURBT specimen respectively (OR=0.87(95%-CI: 0.41-1.8, p=0.7). Conclusion Clinically, DM positivity rate has prognostic significance only in the pT1 category of NMIBC. For pT1 tumours, the positive DM rates for the CUS and SRs were 76.8% and 59.5% respectively. The indifference in the recurrence rate may be due to the considerable proportion of lost to follow up in our study. Nevertheless, measures should be taken to enhance the DM positivity rates among urologists to achieve accurate staging and better prognosis.